Besides that, some of them who might be angry over the death of a fictional character might even have had that fiction as a place and pastime to get away from real losses in real life as well.
That's even more true than you think. In the last 10 years, I lost five family members, two friends, and a colleague. I don't need to be taught the lesson of loss and death, I already experienced it more than I care for.
So
Lynx is quite right in that regard. Writers should be writing books to entertain us, not to teach us lessons about death; real life is a much better teacher than they could ever hope to be.
And forgive me for saying so, but whatever explanation they come up with for killing off Janeway, we all know the primary reason is to sell books. Offing main characters is a cheap way to do that, and people are interested for the same reason they stop or slow down on the highway when they see there has been an accident : to see the blood and gore and be happy it's not them in the wrecked car.