That argument was specifically addressed ('it doesn't matter if a gay person is in the closet, they will be targeted'), but you're ignoring it.
Also, there's a qualitative difference between harassing someone (purposeful infliction of harm on an individual) and mere dislike of their non-harmful consensual activity with others.
So, it's OK to harass e.g. gay people? After all they can stop having sex with men and marry a woman. How about Christians? Muslims? Democrats? All of them can stop being what they are, so it's ok to harass them?
Looks like a half-thought argument.