Two opponents were working together

[katarangi23]

My two opponents in a 3-player game of Catan were working together. They only ever stole from me (despite the fact I was losing), and only traded with each other. Sometimes they re-offered a trade to each other after initially rejecting it (during the same turn), suggesting they were talking to each other outside of the chat. Later I discovered they were also friends on BGA (and they were from the same country).
I questioned in the chat why they were playing that way but they didn't reply and continued their bullying behaviour. So I said I was not willing to play with them and quit the game.
Now I have lost reputation and the only thing I can do is thumbs down them, while they get away with it. This doesn't seem fair. There is no other way to stop this behaviour and if you try to report them for working together it just tells you to thumbs down them.
What else can be done to stop this kind of behaviour in other players? Is there a better way to prevent it? Can BGA rethink how they handle these kinds of situations?
I am not being moderated or appealing any moderation, just putting the issue out there for discussion

[euklid314]

Look at the playing history of those two players. If it was just the one game that you just played then call it bad luck, give them a red thumb and move on.

Otherwise, replay many games of them and look if
*) they play together on a regular basis (especially in 3 player games),
*) regularly trade exclusively with each other,
*) always rob only the 3rd player,
*) make very unfavorable trades that always help the player whose turn it is at the moment,
*) probably even refuse to play the final, winning move by one player in order to always achieve the same of the two players being 1st, the other player being 2nd and the unsuspecting "victim" placing 3rd.

If most of these points are true in a lot of games (30+) then you can report them and they will be moderated. I can confirm that it works - it did for me.

*) Go to the profile of one of the players
*) Choose "Report this player" on top right menu
*) Accept that you may be punished if you make false accusations
*) Choose "XXX uses several user accounts to gain ELO points"
*) Choose "The accounts play against each other to cheat the ranking system"
*) List all accounts that have cheated/collaborated
*) Give a list of all games of those players which did involve cheating
*) Give a very detailed (!!) report about how the cheating happened. Mention series of suspicious moves (be very specific) or give statistics on their trading behavior/usage of robber,...

You see that is quite some work for you to successfully get cheaters moderated. But it works!
It is extremely important that only very detailled reports will lead to punishments/moderations since surely most of the complaints that reach the moderation team are simply not justified and only come from sore losers.
Thus any successful request for moderation must be beyond any reasonable doubt and cannot be based on only 1-5 games.

[katarangi23]

Thanks that's helpful. I guess it is a lot more work than I'll be willing to put in, but it is just frustrating that this kind of thing happens. I do wonder why people choose to play like that as surely enjoying the game is the point, rather than simply finding ways to increase ELO. However, thank you very much for your information which was helpful.

[Jellby]

I do wonder why people choose to play like that as surely enjoying the game is the point, rather than simply finding ways to increase ELO.

For some people, increasing ELO is the game.