I think laws against being gay are wrong, but I have to disagree with your argument that they are laws against existing. You can be gay "inside" but never act on it. That should suffice for you to not get "punished".
A couple might try to stay at a hotel in a room together, but because they are both men it could suddenly become a serious problem. Maybe they aren't even a couple and are two friends trying to get a cheaper room, but they get arrested and have to prove they are not gay.
A couple might want to enjoy dinner together at a restaurant, maybe that becomes a problem.
A couple might have "incriminating" pictures on their phone and be arrested.