My friend and I do paintball competitively and we are quite good at it. We have a plan we follow and we had agreed on this beforehand. For some reason he abandoned the plan and had a tantrum. Without a clear strategy, my friend and I were forced to use dirty tactics to win the match such as 

1) Feigning injury, 2) Shooting people who were already down over and over and shooting people in the back 3) Calling people disgusting names in order to get them to lose concentration

I don't like having to use any of these tactics and I told my friend this. He replied that he didn't see what the problem was as we still won the match. 

I don't know what has come over him, should I start looking for a new paintball partner or is it worth giving it another try?