Depends on whether you think we are still inherently violent animals at our core or not, really. If we are, then sports could be considered culturally cathartic for all the instincts and urges we repress. If not you could argue elevating our sportsmen to high social status encourages violent thuggish behaviour we should have gotten over as a species by now.
I'm a fan of sport, but even if it is cathartic (and if it is, you'd have to argue that you'd be better off playing it than watching it) the amount of money some sportspeople make is ludicrous. There are people make millions of dollars a week for what ultimately amounts to an hour or so of entertainment that they provide us - I don't want to be the person that constantly brings up
all those starving children, but seriously, if you made golf, football, baseball and basketball all strictly amateur or cut down their wages to an amount that would give them enough money to live comfortably (ie. the kind of wage people working actual jobs get) you could buy half of Africa with what you save, and finance the re/building of a sustainable, stable economy with what you've got left*.
I'm a big fan of the strictly amateur leagues they have in Ireland - the players still get to star, they are still idolized, but they aren't being given more money than they know what to do with.