You and I and McConnell might agree, but the congress didnt. Moreover, Trump was calling for everyone to chill when he got banned, which to me indicates really bad risk management on behalf of twitter and fb. They risked further escalation to avoid responsibility.
Congress' opinion didn't matter in this case, Twitters did, and since its their TOS they said he violated, they were free to kick him off their website.
Ever read Shakespeare’s Julius Caesar? There’s a certain speech you might find enlightening if you think Trump was trying to cool things off with those tweets.