Agreed it's crazy, but it's a good political move. Everyone agrees we should ban it, but no one wants the blame because you'll have a huge amount of teenagers and young adults who will blindly hate you for it. So if you're the one who isn't in charge of the hard-but-good decision (or in Trump's case, if you don't particularly give much of a shit about it anyway) it's easy to just pick the most politically advantageous side.