Maybe I should have put this in bold text, you apparently didn't read it.
The talent level of the two isn't close. The significance of it from a basketball/baseball standpoint isn't close. And yes the cultural environment is nowhere near as hostile today to gays than it was towards people of color in Jackie's day.(I'm not equating Jason Collins' situation with Jackie Robinson, just pointing out the flaw in your logic)
But there IS a parallel here.
In terms of a young person of color or young gay person seeing that people like them can succeed in pro sports and overcome adversity and discrimination, they are both moves in the same direction.
I can almost guarantee you that there are numerous players in the Hall of Fame in all the major U.S. pro sports who were gay but never came out of the closet. If Collins' situation can gradually lead to another player here and there going public, and eventually get us to the point a few years down the road where it truly doesn't matter what a pro athlete's sexual orientation is, that will have been a positive thing. So yay.
I don't think anyone can argue that racial integration of pro sports wasn't a good development for overall race relations in the country. I hope/feel that more of this type of thing will have a similar positive impact on LGBT persons' status in the sports community.