How can the US government create anti-domestic terror laws that cannot be weakened [View all]

by the US Constitution?

The January 6th terrorists, so far, are being treated as petty criminals.
I get it. "The Constitution".
However, I don't see how those who carry out coup attempts, and other anti-US violence, are deserving of being protected by a government they tried to destroy.

So, how can this be done? Can an act of Congress do it, or would it require a Constitutional Amendment?