I mean, we're learning right off the bat that this dude is a deplorable, racist asshole. It's getting to the core of a character, not trying to present some view on race from the director.

We also see Costigan's asshole cousin make fun of Puerto Ricans, and Costello later call the chinese guys 'chinks' and make the 'no ticky, no laundry' joke.

I don't see how these moves could be interpreted as the director's feelings. They allow us to gain insights into these characters, in the former case, a low-life loser criminal and in the latter, as I said above, a deplorable racist asshole scumbag. Should they be presenting this with watered down terms that don't cut as deep and in turn water down the characters?

As for the rest of his movies, as much as I hate to say it, being full-blood Italian, it's not like Italians have the best reputation when it comes to racial relations. And in Departed, it may not be Italians, but again, it's not like the Boston Irish have the best reputation with racial relations either. These are depictions of the reality with these characters, not gratuitous shots at black people.

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I'm a free born man of the USA.