[hocus pocus]

The situation you're in sounds very frustrating. Some parents do not realize that many students do curse a lot. I remember my mom was surprised when she went into my school one time because every other word out of someone's mouth was a curse word. I think you should explain the entire situation to your parents.

Explain to your parents that your friend is a close friend of yours and explain some ways he helps you (he's always there for you, you study together, etc). This might make them realize that he is good for you, despite what they think. It might be worth explaining that your friend's cursing was incredibly minor compared to the way other students curse at your school. I think it's worth telling your parents that, while some autistic people are into gaming, gaming as a hobby doesn't necessarily make anyone autistic. Your parents are right in that academics is important, but your friendships are just as important and I hope they're able to realize that.

I know confronting your parents can be really hard but it can help you in the end. If you're not comfortable talking to them verbally, consider writing a note and leaving it where one of your parents will find it.