Well ... first off... so sorry about the fist - I bet that hurt. Who gave it to you?
Seriously - League President has ZERO authority on the field. And in your case, for obvious reasons. But you did right by just leaving and letting other handle it. Sucks you have a League President so clueless.
Coach comes unglued? You toss him right then? Then you can walk away. Don't care if the game's over - unglued coach gets to go to the review board anyway (whatever procedure your league has).
Only thing I'd have done differently (other than tossing coach) was - if he had time to find the CLP (Clueless League President), you had time to be in the umpire's room or at least off the field. Let him argue it with the CLP. Let him file a protest or whatever. You are gone and Home Team has won. Later.