On a pedal building forum somebody posted a thread about how he went to a punk rock show to support a band of a friend of his and where after the show the band members were giving him grief because he used pedals. Because apparently real musicians don't use pedals. The irony of punk musicians styling themselves as real musicians being deliciously lost irony on them as well.
To make a long story short, people have very preconceived ideas about things, especially in regards to identity. And whatever doesn't fit with that identity they'll going to make fun off at best and actually hate at worst. If your identity as a musician is to be able to play a million notes per second, Edge is a hack. If your musical identity is as a straight into a tube amp guitarist then Edge is a hack (although the first U2 albums that formed Edge as a player are basically very close to that). It doesn't help that deep down every guitarists dreams of making it big and playing in stadiums. But 99.9% of them don't even make it to a venue that can handle more then a hundred people. And to see that some hack not only manages to make it big, play stadiums and get his own signature gear, yeah, that does create major cognitive dissonance between their preconceived identities and reality. And expresses itself in virulent youtube commentary hatred. Because even if you are a musical nobody, you can still leave a vitriolic comment and then feel better about yourself. Hmm, maybe not so long story short after all.