Apologies for the long post that largely agrees with what you had to say :p To give some background to the uniniated, the theory of 'Social Facism' as described gives a historical perspective into so-called 'red-brown unity' leading up until WW2.
(anti communist parties described Stalinists as fascist) [...] led to mutual hostility between social democrats and communists, which were additionally intensified in 1929 when Berlin's police, then under control of the SPD (socdem) government, shot down communist workers demonstrating on May Day in what became called Blutmai (Bloody May). That and the repressive legislation against the communists that followed served as further evidence to communists that social democrats were indeed "social fascists".
The idea of social fascism, that social democrats are "objectively the moderate wing of fascism" as Stalin put it, intensified by SocDem authoritarian anti-left policies, lead to even greater hostility from the Communists against the Liberals than the Nazi's themselves at the time.
In 1929, the KPD's paramilitary organisation, the Roter Frontkämpferbund ("Alliance of Red Front-Fighters"), was banned as extremist by the governing social democrats. A KPD resolution described the "social fascists" [social democrats] as the "main pillar of the dictatorship of Capital". In 1930, Kurt Schumacher of the SPD accused Communists of being "red-lacquered doppelgangers of the Nazis". In Prussia, the largest state of Germany, the KPD united with the Nazis in unsuccessful attempt to bring down the state government of SPD by means of a Landtag referendum.
So technically, there was a red-brown (Communist-Nazi) alliance within Prussia in order to take down the SocDems, the Comms were obviously more ideologically aligned with socdems but felt they were the main thing preventing progress and thus wanted to speed up their demise.
We all know how collaborating with the Nazi's turned out:
After Adolf Hitler's Nazi Party came to power in Germany, the KPD was outlawed and thousands of its members were arrested, including Thälmann. Those events made the Comintern do a complete turn on the question of alliance with social democrats and the theory of social fascism was abandoned. At the Seventh Congress of the Comintern in 1935, Georgi Dimitrov outlined the new policy of the popular front in his address "For the Unity of the Working Class Against Fascism". This popular front [...] The American historian Theodore Draper argued that "the so-called theory of social fascism and the practice based on it constituted one of the chief factors contributing to the victory of German fascism in January 1933".
It turns out that by the communists temporarily aligning against liberals with the fascists in what today would probably be known as 'accelerationism', we headed from social democracy to concentration camps in 10 years.
And as you say, fascism is typically more obvious:
Leon Trotsky argued against the accusations of "social fascism". In the March 1932 Bulletin of the Opposition, he declared: "Should fascism come to power, it will ride over your skulls and spines like a terrific tank. [...] And only a fighting unity with the Social Democratic workers can bring victory".
And while there are elements of logic to such a conclusion of 'social fascism' especially when today you have every 'social democrat' or 'liberal' capitaluting heavily rightwards and forming alliances with the far-right (France etc.) BUT As you say, and as history has shown, muddying the waters about the true nature of fascism pulls wool over the eyes of those with potential to affect change and prevent the rise true fascism. Which is growing every day.
Karl Popper argued that some radical parties of the era welcomed or turned a blind eye to the weakening of democracy, or saw a dictatorship as a temporary stepping stone to a revolution. quote from Popper "[Communists] even hoped that a totalitarian dictatorship in Central Europe would speed up matters [...] Accordingly, the Communists did not fight when the fascists seized power. (Nobody expected the Social Democrats to fight). For the Communists were sure that the proletarian revolution was overdue and that the fascist interlude, necessary for its speeding up, could not last longer than a few months."
And finally, it reeks of the unfortunate leftist 'purity test' behaviour which weakens unity and divides potential allies.
In 1969, the ex-communist historian Theodore Draper argued that the Communists who proposed the theory of social fascism, "were chiefly concerned with drawing a line of blood between themselves and all others to the 'right' of them, including the most 'left-wing' of the Social-Democrats."
Anyway, when I read this theory it opened my eyes a tonne to the folly of refusing to collaborate with liberals. While I still believe liberal and center right policy, along with intense anti-left propaganda, are the reason for the rise of fascism today (overton window, ratcheting effect, disillusionment with electoral politics due to ineffective and oppressive governance that only benefits the wealthy).
Despite this by ostracising and refusing to collaborate with liberals we shoot ourselves in the foot by being so obsessed with purity that we reject reality. Perfect is the enemy of good. All progress is good provided it takes us along the right path and does not cut off the path to something greater.
Apologies for the long comment you were fully within your right to haphazardly essentialise about the state of affairs, sometimes we just want to complain. Its just about the audience really, and it can be so difficult to distinguish between bad-faith actors and those who are being snobbish in their response to you when you have the wrong audience for your rhetoric.
It really depends on your audience, unfortunately the majority of people you speak your rhetoric too will not have 10% of the basis in knowledge required to make a consistent logical leap between neatly packaged concepts. Especially when many of those concepts have been prepackaged to the audience as inherently deserving of ridicule. Whereas the core ideas of most of those concepts are agreed upon across the political spectrum.
Its far easier to argue against the Friedman Doctrine, the idea that "The Social Responsibility of Business Is to Increase Its Profits", than it is to argue against capitalism itself in an optics sense.
Again its easier to argue against the current state of things, often colleqioully known as 'neoliberalism' and 'late-stage capitalism', than it is to argue against capitalism. Even if that implies the same as what you said (that capitalism tends towards or has tended towards inevitability), it will be received much more graciously as an observable fact of the current state of affairs.
The Trump camp argues against the current state of things very effectively, despite intentionally identifying the issues incorrectly and pushing them in the worse direction. Because most people can identify the current system is broken, and most want to believe they can help to make it better. If they are given the right framework, debunking common misconceptions, blaming 'late-stage capitalism' for example, corporate elites, info about PACs and lobbying (how capitalism undermines democracy through bribery), then they would hopefully come to the conclusion themselves.
My point being, while its not always your responsibility to meticulously articulate (some of) the core fundamentals of your ideology; if you hope for effective praxis then approaching people where they are at is necessary. Otherwise you risk appearing out of touch and facing (however (un)justifiable) pre-prepared ridicule potentially harming the ideology further through vibe association.
When your audience is non-leftists (liberals), argue against corporate greed and for real social responsibility for wealthy and corporate actors, who should be providing their fair share to society first. Then argue for state ownership of public services, some services should not be ran for profit and instead for maximising public good (public transport, healthcare, energy, water, etc.). Argue against nestles actions in flint for example, or healthcare costs. These are all easy wins, argue against the big monopolies making us pay more for worse services, argue they should be broken up to allow competition.
Like I say though, you are within your right to complain and not explain, just don't be surprised when you have stinky libs acting smug and being arbitrarily obtuse.
Also, don't be dissauded by the humiliation, that is their strongest tool in making us powerless.
I'm reminded of a quote from Yuri Bezmenov: