In quite a few states (my native Texas included), it's still perfectly legal to deny someone employment or housing because of their orientation. I've known people whose landlords threw them out of their apartments for being gay. A trans woman was murdered in a hate crime not far from where I live recently (IIRC, either last month or sometime in May). The fact of the matter is that LGBT people have a history of facing discrimination and animosity. A lot of us go about our everyday lives constantly on guard because of it, and while things are slowly changing for the better, the keyword is "slowly". Not to mention that being told that simply being who you are or having a loving, consensual relationship with your partner is disgusting, perverted, or otherwise somehow wrong is interpreted by many of us as incredibly disrespectful. It may seem harmless, but young people have been abused or disowned by their families because they were LGBT. It's not something that someone wants to deal with when they're engaging in a hobby. When I DM, I'd rather have my players forget about the BS that they have to live with, so I let them be themselves, be excellent to each other, and basically play whatever they want as long as it's not game-breaking. Then there's also the double standard of LGBT content being considered more risque/sexualized than content of straight people doing the exact same thing - for instance, seeing one person briefly kiss another on the cheek. I keep all my games PG-13 (some innuendo and player-initiated shenanigans, but nothing described that goes past smooching), and I've made it clear that I don't have any double standards with regards to what stuff I consider too much to not give the fade-to-black treatment. There's only one thing orientation does affect in my games, and it's whether I decide to kill my PCs with an incubus or a succubus.
