There are some areas/cultures where this is a good thing, because it is raising awareness. In others, though, it is counter productive for the reasons the dissenters specify -- it gives the appearance of trying to make gay people "special", rather than just ordinary men and women who just happen to be attracted to people of the same sex.
There is nothing wrong with the "gay culture" that we hear so much about, but there are many, many gay and lesbian people who are not part of that culture and have no interest in being part of that culture (eg. myself). For this later group, we just wanted to be treated as normal people -- nothing special.
If you try to apply the same idea to other groups, I think you can get a better feel for how this idea can sometimes be a good idea, but other times is counter productive:
Hug a Black Person Day
Hug a Deaf Person Day
Hug an Amputee Day
Hug a Veteran Day
Hug a Politician Day
Hug a Catholic Day
Personally, no, I won't be hugging a gay person on 2nd February.