But it's irritating, unfair and unjustifiable.
It's nothing of the sort. It's a totally normal human reaction. People identify more with stuff that hits closer to home.
People who are talking here are from western countries, many of them from America. We go to sporting events all the time. This could very easily have been one of us. Hell, I have been a spectator at the Boston Marathon. I have run half-marathons. I know exactly what it would have been like.
On the other hand, it is difficult for most people to identify with a plane crash in a country very different to ours, that most people know little about, who has an ex-Soviet airline that has little resemblance to the safe, well-maintained western airlines we use.
A differing emotional response doesn't equate to placing a differing value on the two groups of people's lives. I am sure that Uzbekistanis would have the complete opposite reaction to the two incidents, for exactly the same reasons, and rightly so.