An article from Canadian magazine "Fab" expresses this bizarre little phenomenon very well:
The negative language so prevalent on Craigslist and Grindr seems to signal that the culture of sexual liberation has been replaced by sexual segregation.
Gay sexual oppression is catalogued painfully on the Douchebags of Grindr blog, which sorts prejudiced profiles based on everything from racism and sexism to self-hating homophobia. But even though we see it everywhere, most people are as willing to admit to the exclusionary aspects of their desires as Lindsay Lohan is to submit to drug testing — statements are qualified by “Sorry, that’s just what I’m into” or “No hard feelings, it’s just my preference.”
Sycamore says that while people have the right to say what they’re attracted to, they have a responsibility to watch how they say it. “On the one hand, people are stating their preference, but on the other, these are not neutral terms. If we were living in a culture where everything was the same, it wouldn’t be a problem. But when sexual preference reinforces dominant systems of power in an unquestioning way, that’s when it becomes problematic.”