This is one of the most overused, vague and inaccurate arguments. Nobody is denied from existing. These kind of extreme claims cause more friction than any actual discussion of the issue at hand.
I don't think it's that extreme. There are quite a few people who deny that being gay is real, and is just a mental illness that can be fixed. I would say that sexual orientation is a big part of a person's identity. It might not be "existence" in the strictest sense of the word, but it's certainly not hyperbole either.
Regardless, if you don't like it, remove that phrase from your reading; my point still stands without it.
Ok, I doubt there's really any significant number of people who care to deny these things but I'll rephrase:
If your identity requires acceptance by others for you to consider yourself valid then it's not really your identity at all. If that sounds strange then replace gender identity and sex orientation with religion. Nobody needs to accept your faith for you to have one. You remain fully independent and capable of having whatever identity you want.
This is one of the most overused, vague and inaccurate arguments. Nobody is denied from existing. These kind of extreme claims cause more friction than any actual discussion of the issue at hand.