Risks are comparative, moral panic is not and ignores this. Banning something because it is not 100% harmless is just not something that is done without extra considerations, such as a moralizing. E.g. Pain killers cause significantly more societal harm than puberty blockers but are still widely available.

As to the real risks, time and again it has been shown that the comparative risks of a) receiving puberty blockers vs b) growing up a gender you do not feel you are, strongly points to puberty blockers being a significant net benefit. Those taking puberty blockers rarely regret it; whereas those growing up a gender they do not identify with mostly regret it are are significantly more prone to abuse, mental health issues and suicide.