Though, I will say this study mostly shows which areas employ more sanitized speech, but I wouldn't go as far to say more or less hateful on lines of race, sexual orientation, or cognitive/physical impairments.
That being said... I'm not surprised. I, for one, am not surprised that most of the hate is coming from the Urban/Rural areas. Cities are far more cultural diverse than towns and other rural collectives--as a result, the residents are exposed to these different races, sexualities etc more often and thus naturally grow to accept it more. Even the ones who adamantly hate it, will view it as less wrong when it is something so common place. The number one motivator of hate is misunderstanding and fear(of the unknown, in many cases)--and that is no exception when it comes to race, gender, sexuality etc. City residents get this higher level of "education" in that regard, as the diversity of the city grants longer and more frequent exposures to such things, thus detracting the chance that they'd choose to make a remark about such a thing on twitter or facebook. I mean... there is a reason that the gay capitals of the world are cities and not towns.. people can get together more and feel safer--they build their own little communities where they stick together, and the only ones not of them are people who pay no mind to such unimportant things such as ethnicity and creed. Small towns, everybody knows everybody and people are slow to change... or at least that is what my experience has taught me.