Maybe it's their music you hate, or something about them. Maybe you met them once and they wouldn't give you their autograph or turned their back on you while playing a gig (see the "Show Biz Kids" thread)

Maybe you just don't like the look of them.
Oddly, I'm finding it really hard to think of one at the moment, but I'm sure some of you have ideas?
(No, killing me in the most brutal fashion possible and dumping my body in a shallow grave is
not the kind of idea I was thinking of...)