It is very very common here for people to use the right shoulder as a right turn lane. We have wide shoulders and there would be a lot of pissed off people behind you if you didn't use it. However, if there's no backup, then you wouldn't be in it until you're right at the turn, and you sure as heck shouldn't be just driving along the shoulder (unless there's a hurricane coming and you're evacuating with a million other people. Then all bets are off and shoulders are legitimate lanes. But you'll only be going 5pmh so less accident potential).
Anyway, I get why someone would be in the shoulder, but it's still van guy's fault.