These People Make the Community Bad...
For some background info, this post-lobby chat was from a custom "Definitely Not Dominion" Hide and Seek Game. It was my mistake to play Hide and Seek in a public room rather than with all my friends. Even so, I find the amount of toxicity intolerable.
In Hide and Seek, there are two seekers and five hiders; the seekers have to find the hiders and the hiders can only use CC to stop the seekers. Seekers win the game when all the hiders have 5 deaths and hiders win the game if they can survive until 40 minutes.
However, due to the number imbalance, people on the "hider" side tend to troll more often, break the rules, and verbally harass the "seekers." The seekers can do nothing since they are outspoken.
Basically, it ruins the overall experience for hiders and I can see why Hide and Seek was not a popular custom game mode back when Dominion was still around. It makes me sad to see that people take custom games so seriously, they intentionally create a toxic environment rather than have fun. No IP, EXP, or LP is earned in custom games, so it is not a valid reason for anyone to flame as much as this person has.