Language is for communication and by consensus. There are very visible differences (and whether there are underlying similarities is really beside the point) between the DEA and what most of us mean when we say thieves, and referring to one as the other only causes confusion.
Language is very important, and by repeatedly referring to what the DEA does as "seizure" or "asset forfeiture", this is itself an attempt to shape the conversation. They operate within the State's legal framework, which is why those euphemisms get used, rather than what they'd be called in almost any other circumstance when done by others (armed robbery, theft, etc).
