Deep rooted feelings - This is the root of any hatred, but sports wise, as stated above, it can come from different places, some examples are:
-Being a fan of an opposing team
-Being stubborn about a previous opinion and not wanted to admit wrong
-Envy - (your team is eliminated or is not good, so you want to tear everyone else down)
-Organizational structure/history - (maybe you hate the Yankees bc they spend money, or USC because of sanctions etc.)
I don't know outside of these why you would hate someone/something in something as non threatening as sports, something so insignificant in most fans everyday life. If you can hate a player because of his performance, you are definitely hating on tons of people in your everyday life. Why would you hate Tim Tebow? He is a good kid, he works hard. Non rival team haters are the biggest mystery to me, I have had people tell me they hate the Lakers because "they win all the time", which would fall under the envy category. Winners don't hate winners, they salute winners.
If I don't have these deep rooted feelings, unless I don't understand sports, there really is no way I can hate on your team/players. I don't know how many times I have to tell people "I have no horse in this race", so I can get them to understand I am looking at the matter objectively.