Hey Chris. You can't change people on the internet by force. You don't know anything about the people you play with, they could be 10, 15, 30, 40, mentally impaired, petty thieves, people you would never associate with IRL, anything at all. Trying to force someone to behave a certain way when you know nothing about them and they're on the internet where they don't consider things to be real anyway is pointless imo. All you can do is act how you would like others to behave or not care. You can't force anything in the first place.
But trying to force something by setting another bad example just makes things worse. You don't want people to come on cRPG and see people getting TK'd, that makes the whole community look like shit. The 12.5k thing might seem like a good principle but you probably aren't considering the effect of the tking on the whole server. You weaken your team in the short term by unbalancing the teams, innocent people get hit by mistake (especially at spawn), and newcomers think the community is not admined properly or full of griefers. People might think that they too can get away with tking people they don't like. You might make the guy who owes money take notice and maybe piss him off, but the ends don't really justify the means in this instance. He might even learn that he was justified in not giving the money to someone who will act like that in the game. Fighting douchebaggery with bigger douchebaggery usually doesn't teach a very good lesson
People don't have enough info to make a decision when it comes to things like small amounts of gold owed to someone. So people can't take sides with you in the first place without more concrete proof rather than just some people's accounts of it. You need proof, and then for 12.5k people won't care enough to make a real opinion either way. You could have made a thread about it and put your side and the other guy might have ended up looking like he was untrustworthy, and that might have led to him giving the gold back, or you might have lowered his reputation and you come out with -12.5k but the other guy looks like a thief. Or he might have put his side and you end up not caring so much about the gold.
Anyway play something else for a while, cRPG is a boring ranged fest anyway