Precedent. You don't let someone get away with something simply because they're leaving shortly. Then you can argue at what point is the cutoff. Is it a year? a month?
But aren’t you concerned about the possibility of Trump voters going over the edge after that?
They already have.
How would we be able to tell the difference between that and what's happening now?
Frankly, are you not concerned that by not doing this, you would be signaling that there should be no consequences for this level of corruption, plain falsehood, and ostensibly deliberate attempts to overturn an election?