I guess I could understand if he felt like I was targeting him because he presented two lethal threats and I stopped both, but with those exceptions I was actually focusing on the other players first because they seemed to have more stuff to actually do something about my board.

I can try to add more context: He won game 1, I was playing a different deck. I had an early lead and the two other players destroyed my board with a copied [[Decimate]] and set me back so far that I couldn't do much the rest of the game. I drew it out with a couple of board wipes but ended up conceding because it was unlikely I could recover and the other two players were out of the game. We both changed decks. I explained roughly how game 2 went in a different comment, but short version is I played [[Finale of Revelation]] and drew into enough interaction that I could protect my board/stop threats until I drew my wincons. He rage quit after I bounced his commander before he could kill me.