Give me a single scenario where money laundering should be considered legal.
I can give you many examples where "having at least $10,000" should be considered legal. Money laundering is evidence of a crime, it should not be a crime itself.
And you should not have to report the money you carry if you, for instance, travel.
Where's the fraud? If I want to run a pizza shop and record a million orders to myself that I never actually deliver, so what?
In fact, it's less serious for society if you launder it, because then you're paying taxes on money you wouldn't otherwise pay taxes on.