All I have to say is, since when did piracy go from cool peg legged guys on ships to sweaty Cheetos dusted basement dwellers?
Joking aside, I'm not too sure who is right. None of us have Mangagamers' exact sales charts(I don't believe, at least) so none of us can say for sure how much of a hit they take from this. Niche markets like these are usually built off fan loyalty, so I find it hard to believe everyone's going to cancel their order of a (boxed, keep that in mind, fans love merch) copy of DCIII because Aearu decided to make a fan translation. However, I also don't believe a moderate sized business like Mangagamer would even care unless they have seen some serious losses due to these translations. At the end of the day, I think the best choice would be to realize when to pick your battles and let it go. This won't stop Aearu or anyone else from translating. Unless you're one of those "fight the power" activist types. In which case, go ahead, fight a legal battle. I would.....but I'm really lazy. So nevermind.