I used to watch Bjorn Borg. The story is that when he was a child playing tennis, he once threw a big tantrum a la Serena, Conners or McEnroe. His parents took away his racket and told him never ever to act like that again. And he didn't. He learned his lesson.
We still watched Sampras, Agassi, Evert, et al., back in the day. The only reason I don't watch more tennis is that I've kind of lost interest in it as I became more interested in other things. But a player's bad behavior never was a reason to follow him or her, at least for me.