Why were they so mean to Dr. Smith

Watching the First Five Episodes, I felt the Robinson's, mostly Don, showed Dr. Smith no respect. Okay he was working for another space team and wanted their mission to be ruined but him being on ship was accident and after that he tried his best to right the ship back to earth. They kept bashing him and ignoring him, even wanting to drift farther from earth (going back to earth could have been done before the Robot attacked them...which Smith tried to stop after lift off). Then Don even puts him in freezing tubes and they falsely accuse him of messing up landing rockets. The their hatred for him nearly got them killed when he tried to message about the weather change when they left Jupiter 2 in Chariot and Smith stayed. They would have been better staying at ship. Like he said it was smart he did not go off with those lunatics.