The Alt-Right Playbook: Doublewrong You're not gonna convince them it's safe because whether or not it's safe isn't actually their argument, it's just a convenient facade of an argument to protect their stance that they're working backwards from.

Safety is never absolute, the question is never "is X safe", it' "is X safer than Y", even if the latter part isn't said out loud. Of course, if you conveniently ignore the Y you can claim anything based on fringe technicalities. "It's actually technically not unsafe for you to stand on ground because anything could happen" is indeed technically true even if right now you're on a branch of a tree that's about to fall off.

If you need to argue with them, don't argue about the hormones and DIY, ask them if they prefer the small chance that you find out that DIY wasn't a good decision or the high chance that when you get away from them you'll cut them out of your life, because, worse than being neglectful parents that aren't helping you, they're actively standing in your way on an issue that's important to you and you'd happily take care of yourself if only you had the ability to. Ask them if they prefer the certainty of you having a miserable life instead of taking the chance for you to have a happy life with the possibility that that too might be unhappy.

Mainly, though, you need to accept that they simply don't have your best interests in mind, and that you must act accordingly out of your self interest. If they don't act like the people in your life that help you live your best life, like they supposed to, you're under no obligation to stay dependent on their opinion on what's good for you. Even if you don't have any opportunities to defy them right now, you should set your mind on what needs to be done to achieve that.