That derailleur, however, is beyond saving. half of it is black. I know, black halves matter but, I suggest you ditch that flawed mech. Send it to me for proper disposal.

BTW, I think your mechanic may not be as stupid as some here portray him. As an employee of a shop, if he is, he was reluctant to say, "sure, I can fix that."...given the potential liability issues. There is a slight potential for danger, being that this thing holds your wheel in place. I think he may just have been playing it safe, on your behalf...and his.