Don't fall for the trap. Secession is up to the citizens of that state(s) to decide, external entities i.e. other states, have no say in the matter. They can accept the sovereignty of that state(s) or do something about it(which to me is tantamount to fascism).
If Vermont wants to secede and require all of their citizens to were purple and ride bikes, nothing I'm gonna do about it.
Not falling for a trap, I don’t think he actually understands that the Founders were seceeding from England when they rebelled. The Revolution (rebellion) was the vehicle by which our Founders seceeded.