well, I'm a Gen X'er --> 34 y.o. but you are right that it seems to be ok. I blame the acceptance on television programmes that we were so fond of like Friends etc. Also, once you accept shacking up as normal, then accepting gay marriage is no biggie...
Of course, it was largely the TV programs, as well as movies. I now realize that all of this was done deliberately, all part of a larger plan of those intent upon undermining our society’s Judeo-Christian underpinnings in order to destroy our republic.