I kinda agree with this. Marotta's first mercato in 2010 looked pretty bad because we finished 7th later that season. But in 2012 it turned out that some of those players he bought, like Bonucci and Barzagli, were actually good transfers and in his second mercato he practically built the winning Juve.
I don't expect the same this time, and I doubt that someone out of Zhegrova, David, Openda and Joao Mario will be a vital part of a winning Juve. But I agree with you that it's unfair to "break someone's back" after his first mercato, especially since he inherited a broken team on so many levels.
I won't lose any sleep tho if we get rid of the guy tomorrow already.