I guess I could see it plausible that some “gays” hated the idea of even having it as an institution. That would not be a misunderstanding (let’s factor lies out just as a distraction).
Right. “Misunderstanding” would be something like thinking that the question was whether the individual cared to be “married” himself, rather than about the legality of the concept. This kind of thing happens with people taking surveys, even when the question is carefully phrased to elicit the “correct” answer.