I'm surprised your friends even know about it; my first guess would be that people tend to feel negatively and/or confused by disorders they aren't familiar with, especially a very complex, ambiguous and invisible disorder. Second guess, they are familiar of the prevalence of self-diagnosis among teenagers, and from these impressions your friends label aspergers the "help me, I'm socially awkward and I love to stay at home and play video games" disease. Third, they heard the aspergers speculations from the Newtown massacre and associate the syndrome it with deviant tendencies.
I feel pretty confident about my first reason, the second two are more speculative and were recurring themes during pending-diagnosis web-surfing phase: I posed a question about aspergers anonymity to yahooanswers, one reply I got was I was diagnosed with Aspergers, and it's #######4 if you ask me. I mean, autism, really? Whom do they think they're kidding? ASD is not a real disorder; it's an excuse for social outcasts to fall back on when they fail at life. If you're shy, get over it. If you have trouble making friends, change yourself. Trust me, it's possible. For God's sake....
A general observation I have for people in general: reaching a social life without road bumps and keeping it that way is not realistic, it's hard, and when we (speaking to NT and AS) see conflict and misunderstanding between ourselves and friends, and see less of it among our less intimate friends, we assume "it's easier for them, why can't this be easy for me like it is for them?" For the most part, that's an inaccurate heuristic, the context in which we see casual friends is not a sample size that paints the whole picture of their "smooth" social life. So now an aspie approaches a NT and says, "I have aspergers, which makes my social life difficult"..to which their reaction is, "how convenient, a disease for not having a normal social life...my social life is hard and I still managed to make friends." A life where people just get along with other willy nilly, in my estimation, is a common but false illusion that people assume alludes only themselves; so I don't think social disorders are particularly sympathy invoking disorders. The "excuse disease" accusation is particularly irritating to me, in that people assume we believe social problems are unique to us, they aren't, it's a matter of the degree of difficulty, and the nature of the difficulty. Although the frustrating reality would really fall on aspies who tend to make excuses if that were the case.
Diagnosed at age 24: Answered questions and guided me to helpful resources