It being legal or illegal to be gay is not the only factor, in this day and age even if it's legal or you live in a 1st world country you can still have your entire life ruined by coming out as gay, while the US may have made same-sex marriage legal I still see stories of teens being kicked out of their parents home, cut from the will and abandoned with litterally nothing to them all because they came out as gay, the thought do that must be fucking horrifying so it doesn't surprise me in the least that some people are so afraid of it they start lying to themselves to convince them they're straight otherwise they might just lose everything dear to them.

You can accept yourself as being gay as much as you want but if society and your family doesn't then it won't mean shit.

Does it suck for their partner? sure but it also sucks for the gay person involved, I cannot in good conscious blame all of it on the gay person, part of the blame lies with society and the family they have, you do not grow up naturally fearing to be gay or hating gay people and wanting to hide your sexuality or even lie to yourself, you are a product of your environment.