Marcus wasn't trying to threaten anybody, that much he had already done with the crooks. He was just trying to be.. oh for salazar's sake he was just trying to help for once. Yeah it would look good publically for him to be known as a savior but he wasn't calling the Prophet, or his agent, or his father who often tried to act as an agent. He was just..
Helping a girl.
A pretty girl, at that. Pure too, right? That doesn't hurt...
Marcus said nothing more as Weasley went about delegating what he was going to do. Instead he set about moving the floating glass carefully in front of him as he directed it to a bin to be dumped. Then, he shot a glance over his shoulder at Weasley and cocked an eyebrow.
"Yeah, you're welcome by the way, sorry I did most of your job before you could even get here," he turned away again to hide his smirk and returned to cleaning up a few broken jars that smelled an awful lot like they had been housing mint extract.
Once Weasley had gone he'd turn back to Susan and raise his eyebrows innocently.
"Did you see tha'? Discrimination, hell... he's jus' mad because my boys beat the tar out of his Canons more often than not."
Also, because, Marcus had (on more than one occasion) tried to make his family's life a living hell while at Hogwarts.