"Has this guy never seen what an F4 can do to a fully loaded semi-truck?"
I'm sure he has, considering that's what he apparently spends much of his time doing. I'd wager his goal is to drive it into lower-powered tornados, a task for which that vehicle looks plenty adequate. ~150 MPH winds probably wouldn't be sufficient to do much to that thing, and the steel plates should provide decent protection against flying objects. I don't think anyone would be suicidal enough to willingly drive a seven-ton truck into an F5 category tornado. I wouldn't want to drive an Abrams tank into an F5.
J_A_B