I agree with The Bern about this. They should pay no more than 15%, just like everyone else. This also implies that the roughly 50% of Americans that pay no Federal income tax, should start!
EVERYONE must pay SOMETHING.
Even 1% lets The Poor have some skin in the game. People who pay nothing are only too quick to raise taxes that dont affect them.
And if 1% taxation hurts them, good! That way, theyll feel the pain of a tax increase just like the rest of us.