I found Clara's negative reaction to the Grunt being a grown soldier very strange. This is basically the same thing the Sontarans do, yet Clara has never reacted this way around Strax. Okay, so her anger seemed more directed at humans for basically creating a race of cannon fodder, but why is she getting pissed off at these people? They aren't the ones who made the decision to do this, and the Grunt seems to be a valued team member. Well, at least Commander Nagata wasn't willing to risk the Grunt just to save everyone else.
Does Clara know all the Sontarans are clones?
If she does it, it could be that she knows that all Sontarans are clones and the entire species is hellbent on warfare where as the grunt and it's bretheren are grown by humans to do the "dirty work".
TDLR - Sontarans are grown to be expendible, humans grow grunts to be expendable.