Spot on.
Love and sex is a marketplace. You have to have something to offer the other person. What I've personally found as someone who is morbidly obese is that if a slim, attractive guy is into me, there's usually something about the other person that makes him less desirable or would cause him to lower his standards; they're much older, have an STD, are themselves even heavier than I am, are in the closet and have little experience with guys, are a drug/alcohol user, and so on. (Also, it's been my experience that black people tend to be more accepting of heavy people for some reason - I don't know what's going on there!)
I think it's very rare that you're going to find a heavy person who is doing just fine mentally and emotionally. It's possible that I'm projecting here, but food is pleasure. Hard drugs are illegal; food is legal. Hard drugs are expensive; food is cheap. Improving yourself to be more appealing to others is hard and takes a long time to produce pleasure; food is easy to eat and produces pleasure right away. Even if you really want to go the hard way and improve yourself, you have to stop doing the easy way for a while - and that means not getting pleasure in the meantime. (Unless, of course, you invest in other activities like meditation, a support group, making a clean home, or reading a book, but how lame is all that?! Video games and porn can help, but those only go so far.)
It makes sense that gay men wouldn't like fat gay men. After all, the extra weight is usually not the sign of someone who is emotionally secure and has control over his life. Statistically speaking, obese men are more likely to tire out more easily, are more prone to disease, and their dick tends to be less visible due to all the fat (causing it to look small). Perhaps we evolved to dislike other gay men who are fat in order to protect ourselves from whatever caused them to become mentally unbalanced.
(Okay, I know that's not how evolution works, but you get what I mean!)
I don't like that I don't have a love life, but I understand why and take responsibility. I wouldn't want to have sex with or fall in love with an obese person either. Before I can get what I want from other people, I have to fix myself.
Also, if you're going to go with suggestion # 2 in Placidity's post, I highly recommend going for "straight" (or bi) men who have a proven track record of being into bigger women. Their love of bigger women tends to transfer over to bigger men, too! Tee hee.