Firecage, no need to pull skins or leave, we modders get this crap every now and then. Most of these nasty emails are probably from people who dont have a clue. If youve credited the maker of the plane and/or template youve used if not your own, then youve done all you need to do.
As for the people mailing these nastygrams, if you have an issue, try a mature approach; try TALKING to the person first. If that dont work, who gave you the authority to be the forum/skin/mod police? Write to the owner of the plane/mod/etc. and let them know you may have found someone ill-using their project. Its then up to them to do something about it. Bottom line, if your feeling the need to bash someone, maybe you need to lighten up...