Quite simply, it can be life or death. Again, I'm not being dramatic in my language.
I also want to quickly address what you said about the higher rates of depression and mental health issues. This is going back to something that has come up. There is nothing inherently wrong with being trans, of course, but if you're a parent, you're given the impression that someone is pressuring your child to become trans, and all you know about being trans is that it's associated with higher rates of suicidality, higher rates of homelessness. No kidding, you'll be scared.
This is why taking the temperature down is so important, because that isn't what's happening, but if you think that's what's happening, that is legitimately terrifying.
Yes, we know that it can be life or death, because, of course, forcing someone to stay closeted is what causes those mental health crises and can lead them to feel sufficiently hopeless that they choose to end their life.