There are places, some with a predominately LGBT clientele, many not, where an overweight person may feel uncomfortable. There are also places where a non-overweight person may feel uncomfortable. The issue raised in the article is that there are places attracting primarily LGBT patrons where an overweight LGBT individual may feel excluded. People can debate all day on if the author's weight is the primary reason he feels unwelcome at certain establishments. FTers could probably list many places where overweight LGBT individuals would feel welcome and others where they might not feel as welcome.
People do have preferences when it comes to finding a mate, be it for a short or long term relationship. Businesses are held to a higher standard except in some very specific circumstances, some of which remain controversial.
Concerning needing to promote acceptance within before having acceptance from the outside world, that's something often suggested for individuals and some groups, but is rarely practiced by those suggesting it. Oftentimes, even partial acceptance from outside entities can be helpful for those struggling to accept themselves. Many LGBT people come out in college rather than high school because the atmosphere is more accepting. The author of the article did relieve some stress by coming out. Sure he still has some stress, but the overall burden is less.
My local paper recently published an article about a local state representative who is 6'3" tall and went from 350+ pounds to 202 pounds over a couple of years. This state representative is also openly gay and is well respected in the community. He explained that one of his main reasons for losing weight was that he felt that his weight would seen as a negative much like it has been for New Jersey Governor Chris Christie. While he's always been on the bigger side, the stresses of the past few years caused him to gain weight to the point where it was becoming a major personal issue for him, much like it appears to be for the author of the author of the posted article. While he still likely wouldn't be chosen to be a designer underwear model or let into certain clubs, he's much more happy with himself and ready to take on the world. Some people might feel the same way at 300 pounds, some 150, but what is important is that the person feels comfortable with themselves and has a fair chance at achieving realistic goals.