It won't be long before we find out.

"How will the DC Marxists respond to resolute mass noncompliance? "

This is exactly 'why' the enforcement was assigned to the IRS.

They have practically unchallenged authority and laws, and even have their own court system.

are most people brave enough to reject compliance when the threat of jail time and fines come?

Resort to force. What else can they do except give up power and that will not happen.