The people using them as drug labs should be shot. But the people enterprising enough to make some sort of reasonable use of the trailers (including selling for cash) are 1) not likely to be the sort of deadbeats who've been sitting around collecting welfare all their adult lives, 2) already determined by FEMA to have lost their homes and to be entitled to government assistance as a result, and 3) way, way down the list of people I'm annoyed at for how my tax dollars have been used in connection with FEMA trailers.
The problem with government help has always been that government decides what sort of help is needed and spends taxpayer dollars on that, without any regard to whether the sort of help it has decided to hand out bears any relationship to what's needed. My assessment of the people who have towed the trailers to deer leases or sold them for cash is that they have probably made a more accurate determination than FEMA of what sort of help they need, and taken matters into their own hands -- quite likely after seeing media coverage of how FEMA has destroyed tens of thousands of its own brand-new, never-lived-in trailers.
Similarly, Jabbar Gibson did a good thing by stealing the school bus and driving a load of people out of New Orleans, while FEMA/Nagin/Blanco had their collective overpaid heads up their a$$e$ trying to figure out how to get stranded people out of New Orleans. Often the government's plans suck and are more expensive and less effective than illegal measures resorted to by the same people the government has told us it's using our tax dollars to help.