Clarifying my statement: you don’t ask a plumber about choosing another plumber, or a storeowner about other stores that they compete against. It is in halochos of lashon hara somewhere, I think. You can ask a plumber about a source of materials or about his opinion about electricians.
I hope if he were to say that someone is bad because he hires only satmars, I would respond the same. And “MO” is a way too ambiguous term. I don’t know whether that mashgiach dresses in shorts, does not wear bekesha, drinks halav stam, or responds to her/them. It is just a gratuitous slur towards a large group of Yidden, something not recommended this season.