That's avoiding, end of it.
It doesn't matter if you avoid because you think you will lose, you hate the guy or you just feel like playing your friend.
Reasons are irrelevant, the outcome is the same, league adulteration based on a player's decision.
It's so simple it's ridiculous there's even an argument. How good you are or how many friends you've managed to make playing worm deathmatches with people online doesn't change this. It was clear from the beginning, there is no need for people to think they actually have a case by letting them repeat themselves over and over.
This person here is just avoiding the possibility of losing against a guy he doesn't want beating him, end of. He also admitted it, so why haven't measured been taken yet? give him a penalty for avoiding, set an example and be done with justice warriors who cannot ignore people on a chat because they're self entitled god believing mental dwarves.