Intimidation and polarization, its mixed.
Killing army officers kids is meant to discourage attacks by the army. Some officers may be looking over their shoulders at their personal interests.
It also reduces the public perception that the army can protect the local people from the Taliban if they can’t protect their own. This may reduce their willingness to cooperate with the army/make them more willing to work with the Taliban. Its all about who is seen to be more dangerous.
Also possible that the army will freak out and commit its own atrocities, making enemies that the Taliban can recruit.
In any case there is little downside in such an organization doing this sort of thing as they don’t depend on conventional morality, even by Paki standards.
I wonder if we’ll find that any of the five Taliban that Obama released for Bergdahl were involved in this? Wouldn’t surprise me.
See this Al Jazeera post’s 1,000+ comments for a better sense of public reaction.