This kind of counterfeiting is a lot closer to theft than piracy. I know the guy selling $5 Oakley's out of a shoebox on the street corner isn't selling authentic goods (although I have no doubt that some people really are that ignorant), but I may have no idea that my money isn't making it back to the claimed manufacturer in the case of somewhat cheaper-than-usual NFL jerseys. Chances are I was just trying to get the best deal but engage in a legitimate transaction. Counterfeiting isn't a lost sale so much as a hijacked one. Contrast that to pirating digital goods, where no money is changing hands.
As noted in an earlier comment, I don't think this is a good of efficient use of my taxes. But if the money is going to be spent somewhere, I'd rather it go after counterfeiters (money going to the wrong party) than pirates (no transaction; could lead to one in the future). Given my choice, it would go after dangerous crime, or nowhere at all in the form of a lower tax rate.