It is never black and white, of course. But I can mount zero sympathy for a person who just as easily could have offed himself with a few pills in the hotel room the night before, Instead, he takes down 170 people with him. That's just plain murder (and a convenient one at that, since you don't have to stand trial for it).
Look, this is going to come off more argumentative than it really is, but stop looking at this through your own lenses. I'm not defending this guy, or saying what he did was acceptable or right. Conceptually, I am with you; suicide is a personal act. This isn't "suicide", this is mass murder, and oh, by the way, the perpetrator went too, and you'll notice that no one is defending Adam Lanza as a "suicide".
But the point I'm trying to make is that if someone has lost the "regard" for their own life, and knowing that all the data shows that despite suicides being incredibly painful and traumatic for the survivors, suicides themselves believe they are making the lives of those around them better, how can you expect them to keep the sanctity of some life in the back end of the plane that they have never even seen let alone experienced? In other words, to respect other lives, you have to respect your own first, and that is the one thing that successful suicides are lacking as compared to those that don't.