Unless I missed it, Trump’s attorney did not bring up a due process argument. Colorado’s SC has just declared that Trump is guilty of insurrection, without trial or any legitimate process. Trump, as a US citizen has the right to be charged, tried, to present a defense, etc. Colorado’s action is clearly unconstitutional and must be overturned. Otherwise, turn out the lights, the US experiment is over.
Colorado did hold a civil evidentiary hearing. I agree that is not the same as a conviction.