All sports, games and even academia are littered with talented folks that were a-holes. Whether or not Earl is an a-hole wont tarnish his legacy, it will probably add to it. He isn't forgettable as many other greats can be. McEnroe is a perfect example. He has embraced his attitude, like with the National car rental commercials, and just has fun with it. Earl probably won't ever do that, but that is mostly because outside of the world of pool, people don't know who he is, nor Johnny Archer or Efren Reyes or Mika Immonen or any of them.
The only people that remember pool players are pool players, and I don't think Earl is an a-hole, just an outspoken competitive guy.
People remember Fats because he was larger than life and The Wide World of Sports used to cover pool. Also, pool was way more popular back then. In the end, I think Earl will be fine. If it was more important to Earl to be a nice guy than to win a lot of trophies, he would probably be doing that.