Many if not most people who wish to kill themselves really just want to put an end to pain, and if there was an alternative method to do so they would take it. I think people should be free to end their own lives, but I also think they should first explore all of the alternatives for freeing them of their pain.
If someone wants to die because they can no longer endure the crushing weight of anxiety and/or depression, but find that simply taking a pill once a day, or speaking with a professional once a week will relieve them of that weight, I can guarantee you that they will be very happy to remain alive.
It's not at all selfish to try and persuade someone to explore alternatives. The world isn't a better place with chronically and deeply depressed people in it and I'm sure that there are statistics that can show that this condition has a fairly significant cost to society. The "selfish" approach would be to urge them to kill themselves: one less mopey person in the world to kill the buzz the rest of us get to enjoy. One less lousy worker to screw up the goods and services we buy. One less desperate soul clogging up this forum with pleas for help.
What do you call the action of people who yell "Jump!" to a person perched at the edge of a roof 20 stories up? Encouragement? Understanding?