It's makes perfect sense that dumbledore was gay and therefore was in love with grindelwald. That was the whole reason dumbledore refused to believe that grindelwald was evil, even when it was so obvious.

And no, Rowling never said that she saw dumbledore as gay just to support gay rights. She also said that this was only her personal view of him, and that her readers did not have to think the same way.

I think she tried to imply that they had a more than friendly relationship, but she just didn't do a very good job of it.