I waited to voice my opinion because I didn't want to sway anything the community decided. Since we're past the point where it would matter I think there are important factors to consider.
I'm excited that the US seems to finally be moving in a more realistic direction.
Congratulations! to everyone this will directly effect. It's really fantastic that the country seems to be moving more quickly on this issue than we have in the past on other human rights issues.
That being posted, I would sort of echo the comment by @Jongware -- it's a slippery slope. Support one political issue and you have to be open to supporting others, even if you disagree with them.
It would be nice if the Federal Government outlawed the Confederate flag... Not that they will.. but if that decision were before the Court and the opponents won (keeping the confederate flag legal) would we be okay with the GD.SE logo getting that treatment to celebrate?
What if the federal government legalized recreational marijuana nationwide? Would a pot leaf GD.SE logo be okay?
Make no mistake, I am happy about the recent decisions the court has made (it's odd to have a Court that actually reflects the public more), but I don't really think open political statements belong on Stack sites. It sets a very bad precedence. In reality, I think it was out of place for SO to change their logo. The moment a site becomes political is the moment they start losing members. If that's not an issue, and the user base can use a bit of culling, then okay. But in general, I feel most web sites dealing with technical issues should be as autonomous as possible.
Politics and religion just don't belong here. In general, they only serve as divisive topics.
Just because you happen to believe in and support this issue (as I do) that doesn't mean you'll support every issue which may come up. Tolerance works both ways and it is often my observation that people are only really tolerant of issues they support.