It’s also true. Both in the sense that it’s what they actually believe, and that it’s the stereotype of them. Calling it a choice gives them the excuse to label homosexuals as willfully evil and persecute., beat and kill them. Just as labeling it a mental illness gives them the option to medically persecute, torture and kill homosexuals.
All that changes it what excuse they prefer to use to justify and enable their fundamental bigotry and malice - the core values of conservatism, in all times and places.