Not that I disagree, but to play Devil's advocate for a second...

I think DHH was trying to refer to junkies and homeless people most of whom happen to be immigrants. The immigration status is the particular attribute that invites usage of the term "gypsies" to signal that the problem with those particular junkies and homeless could be solved via immigration enforcement. At least in his eyes, I presume.

Again, not defending his choice of words, just providing a somewhat plausible explanation as to how one might arrive to this specific terminology.