The idea that suicide is selfish has always, honestly, made me feel sad for the people who say it. That's the (understandable) anger and hurt response of the people left behind.
Having been at that point myself, and talked with many other near-suicides, I can safely say that being selfish is the last thing on your mind. For most of us, dying was the most *selfless* thing we could think of doing. Not only were we trying to end our pain, but the pain of the people around us who had to 'deal' with us. How much better the world would be, were we not in it!
Suicide is a breakdown of the self-preservation instinct. How a person gets to that point varies, but I've explained it like this...
Imagine you're walking a road, and the road leads to an arid, barren land. There is nothing but dry, empty wasteland as far as the eye can see. Occasionally, unexpectedly, there is an oasis, and you can rest there, but eventually the call of the road always sets you to walking.
So you walk, focused on the empty landscape streching out endlessly before you. You grow thirsty, hungry, weak. Every step is a struggle for body and soul. Suddenly, without any warning at all, you find yourself steps away from a bottomless chasm. You turn to go back, and are confronted with a seemingly endless wall that has spring up behind you. You may hear voices urging you to safety, feel hands reaching to pull you over the wall, but to you they are ghost sounds, mirages of the heat and your mind.
Trapped between wall and chasm, you must chose...claw your weakend self over that wall, or step into the abyss.
That's suicide. And really, only someone who's been deep into that wasteland can understand it. Some people come back and fight against anyone else wanting to die. Some of their methods are effective, some of them aren't, and hold echos of the hurt they felt, and the anger that was projected onto them by the people around them.
And some of us see somoene wanting to die, and nod, and say "We know how you feel. We can't stop you, it is your right, but know that you aren't completely trapped." Maybe they will hear our voice as they stand by the chasm. Maybe we can find the sledgehammer that will break through their wall.
Suicide is selfish? Sometimes my response to that is mindnumbing *anger*. How dare they judge us that way. How much more selfish is it to tell someone they must be in pain, they must ache, body mind and soul, just so you won't lose them? Are you at the core of their hurt? Do you know why they want to die? Then don't presume to know what motivates them into that chasm. Do everything you can to help them back from the edge, but guilt and blame and anger is *not* the way to be heard.