I've always hated when people brought up the "imitation is a form of flattery" and all that jazz. In elementary school, kids were always copying me (mainly in creative things like art or writing) and once I even cried after my teacher said that the kids were complimenting me by copying my artwork.
It's flattery, it's just plain rude

And it sucks when fan things get stolen since they tend to be a bit harder to get removed from sites. Best of luck, though.