If Ludwig were alive right now, I think a lot of people would be calling out about interesting assumptions. I do think it's a little rude and presumptuous to speculate about the personal lives of anyone - alive or dead - when it really isn't any of our (in the general sense) business. That's how I try to look at things.
But people do speculate about the love life of for example, Henry VIII, when they visit a place historically connected with him. Or of Marie Antoinette. So I agree with PaddedPaws that whether one considers any speculation about the private lives of historical figures appropriate or not (without going into the issue that most historians find private lives a very important part of history), the fact that his speculation is of a homosexual nature does not make it any less appropriate.