A type of unit that is usually found in trader clans. Their name is a nice way of saying that they look for parts to steal from free teams, if anything desirable is spotted. Sometimes, even members of free teams own valuable equipment, after all. And just killing them and taking that equipment is free, as opposed to having to buy it off them.
In my defense, I think most people would have reacted this way if they came to a trading post and these guys tried to sell you your own parts.