Those who support unconstitutional overreaches by the federal government are perhaps not considering the unintended consequences of eroding the principle of governing in accordance with such constitutional limits. They ought to consider a type of government restriction that they oppose and find harmful, and consider how much worse it is when the federal government can nationalize it.
Second, once someone reaches the age of consent, they should be able to do things that run a high risk of ruining their lives. The only type of restriction that I could possibly see being justifiable for activity like this is on advertisements for such activity, which could be required to disclose risks and/or not communicate falsehoods.