Did you miss the part where the OP was not mentally ill, and only mistakenly believed to be so?
Or are you assuming ignorantly that being transgender is a mental illness? Even if it was, Transgender folks are no more likely to be public safety concern then you or me, but are about 1,000 times more likely to be a victim of violence and in need of the means of self defense.
Besides, the climate change folks seem to be doing pretty well with an actually mentally ill young person championing their cause, so whats your concern exactly?
Do you have an issue with people with mental illness (a term so overly broad as to be mostly useless in public policy discussions) or with transgender people owning firearms? If so, who else are you comfortable discriminating against?
Any person who is laughed at for their personal history and denied their rights in seeking a firearms license application is perfectly suited to go scorched earth on the ignorant government bureaucrats who are being discriminatory and to make that experience as public as they like, and all of us should support them 100% in that fight, as it is all OUR rights that are being infringed. Only thing is they happen to be the victim, this time...