I think the issue is that he's so out of control that his own campaign had to lock him out of his Twitter account..
Basically, yeah Obama has had the power and hasn't used it, but the thought is that Trump will not be able to resist the temptation to be able to directly message every cell user with unblockable text...
Also, I've already seen several excellent posts helping people block unwanted Amber alerts and some folks offering advice on rooting phones to allow that to be shut off.
I'm willing to take a wait and see attitude, but if he sends one of those texts and it's not because the Great Meteor we've all been hoping for is on its way, I'll consider rooting my phone if there's a way to block the Presidential Alerts.
He gets ONE chance on that.