Technically yes, it is Malcolm's issue. In all fairness, he might actually be decent at sign language since he talks with his hands anyway. It's not like he's good at any spoken languages other than English.

He sits down across from the other man. "Okay, sure." No need to slow down his speech. "Did you come here of your own free will?"

Now that he's sitting down, Malcolm gets a better look at the guy. The jacket and the sideburns could mean that he's from the 70s. Or they could mean he's from Williamsburg. Hipsters all have their own thing.