Taxation is a necessary evil to fund those things the government must provide. It is not some social tool to seize all money above some arbitrary amount just because muh rich people are icky. If you can set a maximum wage at $45 Million, you can set a maximum wage at $5 since its all arbitrary line drawing.
This argument is just dumb, even you must realize it's weak as hell. The government passes one law that's not that objectionable, but that means they could also pass a crazy law! I mean, yeah, or government could enact a crazy law right from the start. It's hypothetical, it's not going to happen though. It's like saying "but if the government passes a law saying it's illegal to put poop in a can and sell it as chicken soup, they could also pass a law banning food!"