I don't have a problem with Sulu being gay, but I would have really preferred another character for it. Giving specifically Sulu likely just a little scene about it, is really a save choice. They take as little risk as possible, while at the same time praising themselves for being so progressive. They do so little, that I bet it will hardly stop any homophobes from watching the movie, because it will be just too insignificant in the greater scheme of things to stop them from watching a movie they otherwise are interested in.
In today's time when quite a few series have well developed LGBT characters, making your most minor main cast member gay and give him a little scene or maybe with some luck two, is the opposite of bold. It is just doing the minimum. I expect more from Star Trek.