Yeah, I don't get the vitriol for U2. I dig that many people aren't moved by the music and many find Bono to be a headline-seeking, messianic (sp?) bonehead, but I'm not in either camp. They were one of the "underground" bands I discovered on my own when Boy came out way back when, and they had a huge hand in me becoming a fan of Television, who they have consistently cited as a major influence. They've put out a couple of albums that I'm not crazy about, but for the most part, I think they are remarkably consistent and certainly a thrilling live act if you can deal with the bluster.
Ashlee Simpson, on the other hand, is almost as cringe-inducing as her sister for entirely different reasons. Me no likey. However, I do not hate her as in I think she's an irredeemably vile human being. I don't know her, just her music and public persona. That, I do have a problem with.
As to the matter of good taste/bad taste, certainly you judge others taste in music, film, literature in comparison to your own, and I hardly see how one could help that. However, I've moved far beyond making value judgements about people based on the music they listen to... well, mostly. I think I'm naturally more inclined to find bonhomie and friendship with someone whose tastes run similar to my own, but I don't write people off if their tastes are different. I sometimes can't help being puzzled, but live and let live, ya' know?