How can I keep people from thinking that I am NOT gay under these cirstances?

Ok, so I am a 28 y/o guy who has never had a g/f in my entire life. From 2000 to 2005, a.k.a. form age 18 to 23, I was in the Marines and was stationed in Jacksonville, North Carolina where there are ZERO single women and where the civilians surrounding Camp Lejeune in cities such as Greenville and Wilmington, NC hate Marines. Furthermore, after getting out, I had to move in with my sister and her now ex-husband so that I would have a place to stay and had to work a low paying factory job so that I could establish residency in Colorado and obtain in state tuition here. Unfortunately, people here in Colorado Springs, Colorado, especially the women, are NOT friendly at all and are indeed VERY rude and stuck up. Needless to say, I've been single the whole time that I've been living here due to these stuck up and unfriendly women. I have just started to loose ANY interest in ever having any sort of relationship with the female gender because of how I have been treated by women here in this azzbackwards city. I will be transferring to a four year university at the end of the year somewhere back home in the southeast or in Texas, but I realize that I will be too old at 28 for those younger women. My main question is this: Since I now know that I will be single for the remainder of my life, how do I keep the small minded idiots that I will be working with in my future career from thinking that I am gay and making snide remarks behind my back because I will be the guy in my early 30s "who isn't married with kids so he must be gay"?