It doesn't matter what they think because they are wrong, just like people who do not want gay people in locker rooms of their gender of attraction. We as a culture has decided that they are wrong, hence people who are gay are allowed in locker rooms of the sex they are attracted to.

The reasons to ban them are moral panic and outrage based around cultural constructs that served arbitrary rules. The gays are sexually attracted to their gender, therefore negating the reason to have separate locker rooms. Emotional arguments defending arbitrary social rules that are harmful for gay people and now trans people. People still are uncomfortable with gay people in the locker room, but they have to suck it up because their view is unreasonable, unfair and supports arbitrary rules that empower a certain group of people over others.