Do you believe that people can be gay? If so (assuming you're not gay yourself) what makes you believe that others can be, when there is clearly no actual proof?

It's funny that this person says this, because there is proof of people being gay but there is no proof of gender identity.

By definition, being gay (and bisexual; LGB generally) is a phenomenon that can be objectively measured. There are two ways I can think of measuring it, off the top of my head:

• biometric data-- this tends to suck for women, as sex research usually focuses on men and neglects (edit: typo) women, but for men, you can literally measure same sex attraction with phallometric tools.

• behavior-- you can observe, behaviorally, whether someone engages in sexual activity with the same sex.

The latter, in fact, is part of the reason why we are so discriminated against! Because throughout history, straight people observed our behavior and they didn't like it. It's that objective. You don't have to suspend your disbelief in order to know that same-sex attraction exists, you can observe it.

Meanwhile, gender identity by definition is entirely subjectively experienced. There is no way to objectively measure it. Just like the Holy Spirit concept in Christian religion. It is believed in by dint of faith alone.