I have never seen a need for that word because we are all Cowboys fans with differing opinions. That doesn't make anyone a hater. If I don't agree that a player is as bad as someone says, then I'll present an argument for why I believe that player is better than that. If something is unfairly being used to prop up a player, then I'll point out why the argument isn't fair. At one point of time, this was simply called a discussion.
Those who are unable to have an open discussion resort to things like name-calling, and hater seems to be their favorite word if you disagree with them. It's a sad thing that is reflected in too many aspects of our society. In general, though, it does help me to see who is just arguing irrationally instead of actually being willing to debate the merits of a post.
Rather than swearing off using the word hater, which I believe most who would take that pledge already rarely use, I think a better movement would be a blockade of those who use the word. In other words, if there is a discussion about a player and someone comes into it and calls someone else a hater, then no one responds to the name-caller for the rest of the thread. Eventually, such a boycott might have the desired effect.
Our tendency is to just fire back, which just fans the flames, when it's likely best to let "hater" speech just die on the vine. Most of those who use the word are trying to provoke, so maybe we should just not take the bait.