Sorry this is happening.
But I don't think it's a great idea to post pm's between you and another party if they were supposed to be private between you two. Did the other guy agree to this? It's far from illegal ofcourse, but it's bad form because the dude probably has no idea and can not join the conversation. Or he gets contacted/bothered by people, which he obviously doesn't like.
I think that if you love the project they're doing, you should probably not do this. I know you're upset, I have no idea what transpired to make them react with such a big warning, etc., in this context it seems very abrupt and a bit extreme. But I think you should not let it escalate like this if you can.
I understand you feel wronged and I sympathize, but this can only make it worse for you. You seem to want to do anything you can to help out with this kickstarter/project, but you may lose this oppertunity if this escalates.
Good luck, I hope this gets solved without too much of an issue.