50 Cent:
Repeated homophobic posts through his Twitter feed.
Kanye West:
"I'ma let you finish..."
Glenn Danzig:
Tried to cut the other musicians out of band royalties and pay them a flat fee as "studio musicians" for the first Danzig album, North Side Kings incident, etc.
Does a performer's off-stage personality affect how much you like / dislike their music? Above are just a few examples, but there's plenty of others, both positive and negative.