Why do they even think that way? People a different. There are all types of people in every group. Even in your own immediate family, our siblings are different from us. In my family, my two younger sisters and I have been more responsible toward our parents than my five other married siblings. Does that make us better children than the others? No.
Some single gay men are very responsible. Some are less. Just like with the gay married men. If I said that single gay men are more responsible than gay married men because they refuse to hurt another human being by marrying a woman to shield their sexuality, would that make me sound stupid? YES!
And, to say that gay married men, as compared to single men, are more masculine and less childish is just like saying Asian men are bottoms. Hell, try reading the blogs by married gay and bi men, you'll see how feminine these people can get. It's a huge display of feminine qualities. Do I think it's bad? NO. To each his own. Do I picture some of them as sassy feminine men? Sometimes. Do I think they are bad people because of that? NO. To each his own.
Just because some gay men choose not to get married, it does not mean they are immature, irresponsible, lack of life experience, or feminine. It could be because they are mature, responsible and have enough sense in themselves to choose not to get married. I bet you a lot of those naked male pictures posted by the gay/bi married men are of single gay men. Do I see people drooling over them? YES. My sister has a friend who is as feminine as one can get, but he is actively seeking to get married. He doesn't think he's gay. I'm waiting to see if suddenly he'll turn masculine once he gets married.
All that said, to some gay married or ex-married men out there who are seeking love, be a little open-minded. You might be surprised that the best person that comes along your way might be one who has been single.