Though the AIDS Coalition to Unleash Power (ACT UP) does have a very important cause, I think that they are hindering their cause more than they're helping it. Why? It's difficult to reach and have an impact on a large portion of the population when you behave like a leftist 'fringe' group. Their website, for instance, has a lot of past and present president bashing, some name calling and some, I would say, stretched claims. It's very important to deliver a message without resorting to these things.
As for how it affects the GLBT community, I said groups like this hurt the community more than they help. It's important to achieve change through mature, informed, respectful discussion and compromise a little bit. I don't think that groups like ACT UP do that to the degree that I would like to see. I realise that AIDS is a global epidemic and immediate action is needed, but effective, long lasting, important change will take place slowly and in doses. Trying to speed it up will paint you as an extremist, and people won't take you seriously.
I'm not implying at all that ACT UP is an extremist, useless group, by any means. I just don't think the change they're trying to make is going to happen through their means.