I think hate can be both a choice and in some ways taught. But I think with the type of hate you're talking about that it's mostly chosen. People can be brought up in a way as to encourage them to hate a race or a religion or whatever, but there's enough information out there for people to make educated choices. Those who don't simply are ignoring the data and making a decision by their own free will.
Some hate is good like:
Hating the St. Louis Cardinals
Hating the Greenbay Packers
Hating the Minnesota Vikings...get an out door stadium you Sallies!
Hating Payton Manning...you played ****ty in the Superbowl and the only reason your punk ass has a Superbowl ring is because Grossman lost that god damned game! And get off the damned TV!
Hating Eli Manning....damned punk, not even as good as his good for nothing brother.
Hating the NY Yankees....god baseball needs a cap
Hating the Chicago Whitesox....south side sucks!