At the end of the day, it's not hard to determine why U2 has a passionate legion of haters:
1) They sing songs about God and large social (I hesitate to say 'political') issues.
2) They're very post-punk.
3) Bono.
4) They're too popular and have been for so long.
Reason #1 is uncomfortable for a lot of people. While I disagree completely, I can understand why some people don't like that. Personally, I don't like Bono's onstage speeches (I call this redundant didacticism -- preaching to the converted), but, you know, he's been around for a while, he can do what he wants.
Reason #2 is why older people like George Harrison and my dad don't like them. My dad is enthralled watching Eric Clapton play a 12-bar solo for three minutes, but at the drop of a U2 song he falls asleep. Why? Because some people of the 60s generation are so beholden to the blues and traditional forms that they can't appreciate the post-punk mentality and ethos at all. U2 are not great musicians, don't care about guitar-solos, don't want to sound like traditional R&B guys . . . and yet they go on about how they love those kinds of musics and people. This was what got them into trouble on Rattle & Hum.
Reason #3 is a strange one -- Bono offends some people's sensibilities because he's too much of a do-gooder who talks a lot. A lot of people aren't offended by do-gooders, but they're offended by people who talk a lot about themselves. And Bono is both. I respect him for that because he's obviously intelligent enough to know that any rock credibility he had (if he ever had any after the mullet) goes out the window as soon as he talks about human rights campaigns, etc., and yet he goes right on doing it. But for people who prefer their musicians simple, humble, and focused on music, Bono can seem too much.
Reason #4 is the most obvious thing -- the bigger you get, the more people want to knock you down. And U2, against every conceivable career curve known to rock, has never really been taken down. You can see people's desperation for this when Pop failed to set the world on fire (only 7 million sold!), and the non-U2-friendly parts of the rock press acted like they had released Metal Machine Music by Lou Reed. I seem to remember Britain's U2-hating music press mag Melody Maker giving the album a 0 out of 10 rating... This kind of thing in itself proves that U2 have reached the stage where they are larger than the industry, and we cannot take any printed review seriously anymore because everyone comes at them with so much knowledge, experience, and opinion that no one's perspective can be objective anymore.