One other thing I've seen argued is that Congress did not proceed with impeachment against Richard Nixon after he resigned, so why proceed against Trump even though he's left office? The matter is moot!
This is correct in regards to Nixon, but not Trump. Nixon resigned (thus removal was moot), and this occurred during his second term (making disqualification from office moot because he was term-limited).
Trump can't be removed, but he is still eligible to run again: proceeding with conviction can thus be used to disqualify him from office in the future.
One other thing I've seen argued is that Congress did not proceed with impeachment against Richard Nixon after he resigned, so why proceed against Trump even though he's left office? The matter is moot!
This is correct in regards to Nixon, but not Trump. Nixon resigned (thus removal was moot), and this occurred during his second term (making disqualification from office moot because he was term-limited).
Trump can't be removed, but he is still eligible to run again: proceeding with conviction can thus be used to disqualify him from office in the future.