If the futures and Men's Opens level is anything to go by, there are quite a few gay players.
But in this day and age, especially where the majority of players are from Europe, it doesn't matter anymore, imo.
If a gay player came out, most people would be like: "Ok, so what?"
We're not in the 1950's anymore.
I am not sure about that, there is a perception that Europeans are more open minded about homosexuality but the truth is this isn't always the case. Maybe, from a legal perspective but not from a social perspective. Right now in France and England there are a lot of anger about the potential gay marriage laws being passed. Also, in European football there is a lot of homophobia and racism where opposing teams make homophobic chants.
The American soccer player Robbie Rogers quit competing in European football because he said the lockeroom is very homophobic and the straight men are very anti gay.
If it didn't matter why are the gay male tennis players hiding in the closet? There has to be at least five ATP players ranked in the top 100 who are gay. This is a fact of statistics there are probably more than five gay male players though.
Tennis is an individual sport, it isn't a team sport so the players have freedom to do what they want they choose the events they want to compete in too.