while what you say is reasonably true, the real reason for taxing the
very rich very heavily has NOTHING to do with money to the government,

Taxing anybody has NOTHING to do with money to the government.
The government doesn't need money from anybody.

The govt needs to tax only to keep the private sector from
spending too much.

The private sector spending too much is not currently a problem.

In 2007 the private sector spent 4 trillion more than
their income. They accomplished this over-spending by borrowing.
In 2010 the private sector spent $2 trillion less than they earned.
That means they didn't borrow and they saved and paid back old debt.

You don't need to look any farther than that decrease in spending to
explain why 15% of people who want jobs can't find a full time job.

The unemployment situation would be fixed almost immediately if
the federal govt just stopped taking so much in taxes.