You can't front run as a market maker, because a market maker literally cannot have clients. Thats like the first rule about market makers in most regulatory environments. Saying otherwise excludes you as a person who knows anything about the details here.

A parent company could operate both a market maker and agency/broker businesses side by side. Leaking information from the agency/broker to the market maker operation is illegal.

Perhaps you think I am nitpicking here, but the point is the bad guys in OPs example are the broker/agency which illegally sell/give away their clients information. Their illegal behavior is not predicated on the existence of the market maker. The market maker is simply an easy bogeyman for people who don't know what the hell theyre talking about.