If the father takes his son into the armed camp of the enemy, behind enemy lines, and the son is killed in a strike on the enemy, I suppose that is killing the son for the sins of the father.
It is a bit of a stretch. This did not occur in a place where warrants could be served.
It's true that they were outside the US's jurisdiction; however, it's the justification offered that is so... unjust.
I also hesitate to point a finger saying he was palling around w/ terrorists for two reasons: 1) if he were then Gibbs would not make main point about the father, but about the terrorists; and 2) the government's willingness to label near anyone [who the government doesn't like] as terrorist {ex Tea Party}... this reediness to do so robs the term of its meaning and makes it utterly useless.