Realistically, I've seen it happen more than a few times in the almost twenty years I've been flying 121 ops. Recently, I've seen it happen twice. Point being, the Labor Dept can beat their drums about this issue all they want but they won't lift a finger to help out the little guy. The cards are stacked in the Employers' favor and realistically the probationary employee better not be spouting off negativity or they will be fired. So yeah, implying a positive attitude must be displayed (or you'll be canned) is a reality.