There is nothing in our Constitution that forbids the impeachment trial after the President has left office
Really? Let's go to the text:
US Constitution Article II Section 4 said:The President, Vice President and all civil Officers of the United States, shall be removed from Office on Impeachment for, and Conviction of, Treason, Bribery, or other high Crimes and Misdemeanors.
Clearly he must be in office to remove him from office, mega fail
bearing in mind that Trump was impeached for inciting an insurrection while President
A direct lie. Incitement means calling for violence, not saying something people don't like. The first amendment covers that.
And you're just a liar anyway. If Trump met your standard, you'd call for cleaning out the Democrat party leadership who all far more directly called for violence