I think you are opening a can of worms with this question, my friend, just to let you know.
To answer the question, I would say that no, it does not make him gay. Then again, that is the opinion of another gay man and I am sure others will say that has a lot to do with my opinion. Truth be told, the only one who can truly know his orientation or preference is him. One act, either way, does not set his future in stone. I don't believe there is anything wrong with a little experimentation.