Is it normal to be judged because of what a "friend" does?

It's quite a long story, so brace yourselves.

When I started college, I met loads of new friends during fresher's week. My "friend" and I were talking one night on MSN, and he asked how I was settling in. He's a bit mentally challenged, and he has trouble making friends, so I thought I would invite him to the next party to give him a bit of a boost.

Fast forward to the party, I'm going around introducing him to all of my new "friends" and whatnot, but the problem is, he can't handle alcohol period, he gets tipsy off one beer. He had about 6 shots of rum (I take some blame here, because I sort of encouraged him to drink with me), and I was pretty wasted myself (again, I take some of the blame). Next thing I know, he's going around telling everybody he wanted to kill his ex girlfriend and her boyfriend. The next morning, everyone kind of takes a giant step back from me, and someone finally told me today that everyone stopped talking to me because of him, that everyone automatically assumed I was batshit crazy like the way he presented himself.

I guess it's my fault for failing to be responsible. Heh.

But if something like this happened, would you be the same as everyone in the story?