Cryptocurrencys by default don't belong to anyone, so karmacoin doesn't belong to you. It doesn't matter what you say, those people are free to do as they please, if they have in fact trademarked or copyrighted karmacoin, now it is actually theirs.
Think about all of the people who invent a product, only to have it scooped up by someone else, who patents it. Guess what. The patent holder now owns the invention. Looks like you just got scooped.
That is true. If he really wanted to cause a fuss, the law would side with us because he would be using our logo without our permission (the one I paid for out of my own pocked and am holding the copyright to); and using our "Karmacoin" trademark that we will have already applied for. Karmacoin is an open source project that he has already made public domain.
But there's no need for such behaviour. We tried to communicate with him reasonably, but he just continues to act this way. It's sad.