They might think that they're protecting you, but you'll need to learn for yourself who is really your friend and who isn't.
It's also possible they're being mean, intentionally or not.
Me, I'm probably only a little autistic. I talk a good game, especially one on one. So when I was back in school, I managed to have one friend from just about every clique. One who took the time to talk to me and realize I was cool and had something going on.
And I treasured that. I knew I wasn't an unlikeable person, doomed to a lonely life.
So don't let your current friends gatekeep you from making more. But be careful and don't let people take advantage of you either. There are mean people and then there are dangerous people.
I only say that on the off chance that your friends know what they mean when they say "You can't be friends with them."