Some of it may be attributed to changing social attitudes in the younger generation(s), but I believe that a change in the way that the GLBT community has marketed their campaigns is a larger factor.
In days past, it was common to get in peoples face and demand equality. Doing so only caused people to back off, get defensive, and ultimately oppose the message that we sought to spread. A better strategy, and one that seems to be increasingly more common and effective, is to portray ourselves as your average, ordinary family who simply seeks equal protection for ourselves and our families. We needed to shed the flamboyant, in your face image, and build an image that others can relate to. One that adheres to "family values" that straight people don't fear will corrupt their kids. As long as we're not perceived as a threat to their families and their lifestyle, many are more open to support our cause.