I like it - as others have said, closeted gay men were around at the time, so why not? And let's face it, TPTB never would have been allowed to publish a gay hero back then. The stories that featured Alan back in the day didn't really get into heavy characterization, so it's not like we had been inside his head and following his life the way we do with contemporary heroes who have a title. He's mostly been featured on teams anyway and there was even less room for personal lives there so it's not like this retcon changes all of his previous appearances. How he deals with or had dealt with Todd would be different though. I don't recall any particular stories about Todd's sexuality where Alan's behavior would have been different, but nothing's really canon anyway - we don't even know if Todd exists.
Also, would it be totally inappropriate to say that at least we finally have an explanation for his outfit....??