Instead of dodging, the people involved should take the person who threatens to intentionally feed (or otherwise grief) to the match, play the match and report him after the match. It might be near guaranteed loss, but at least that way the griefer would be reported and might one of those days even be punished. Also, as long as these griefers are "evenly spread" to both teams, the properly playing person's team will have statistically less griefers than the enemy team, so his enemy team will have griefer more often than the player's own team. (Rationale: Enemy team has five potential slots for a griefer, ally team has only four slots - therefore ally team has smaller chance to have a griefer than the enemy team).
Tl;dr: If someone threatens to grief, take the bait, play to win, report him and potentially get him punished.
PS: And Riot please do your job. Many of us players are getting annoyed by your lack of (visible) action.
PPS: Oh, and now that Riot is reading this (yeah, sure): Please remove me from the false reporter black list already. I haven't seen "player has been punished" message in over two years and I still meet bad guys who need punishing regularly. Maybe check that your EUNE support personnel are actually doing their job while you are at it? ;)