I never said to shame someone. I said it was selfish, which it is. But that doesn't mean you go and be stupid enough to say that to a person threatening to kill themselves. Have some common sense.
Saying something in public to people that may or may not be suicidal is no different than saying that thing to someone who is suicidal. It's likely, considering the statistics and how many people read this forum, that you just said that to a person considering killing themselves.
When you define suicide as inherently selfish because you're thinking about yourself, you ignore the connotations of selfish and the meanings that go beyond the word in our world; those can't lightly be put aside and ignored. In a world where no one had emotions and everyone used words strictly according to their dictionary definition with no nuance, the word selfish wouldn't be insulting. People would recognize that most things done in life are selfish, that if you eat every day and have a home you are inherently selfish because you're keeping these things instead of giving them to the people starving to death and that's not bad, just life. But we don't live in that world, unfortunately. We live in a world where calling an act selfish is the same as calling a person ugly - technically it's a neutral word that has a meaning and passes no judgment, but in reality it is much more.
Being suicidal is a symptom of mental illness. Your analogy doesn't actually work, unfortunately. The only time the concept of suicidal as mentally ill is thrown out the window is in the case of euthanasia due to terminal illness. The vast, vast majority of the time, suicide is the result of mental illness, when without the illness the victim would be able to see the irrationality of killing oneself in a world with some friends, some family, and a life beyond whatever is driving them to suicide.
I'm not sure how your friends leaving therapy is relevant, honestly. I do know that there are good therapists and bad therapists, and those that are open to moving past their illness are challenged by therapists and respond positively. However, therapists undergo years of training to find how to push those that need it to be able to heal themselves. We do not, and that is not our role in a person's life. In addition, I have heard horror stories, such as a transgender friend of mine that went to a therapist to get her "mental proof" that she was transgender and was subjected to a series of questions about which gender stereotypes she identifies more with to determine if she was really a woman. This is getting a bit off topic because I'm not sure how to respond due to my inability to understand the connection, so feel free to fill me in and I'll come back to it.
It's a common misconception to create the binary of how to treat people, either telling them that their actions are selfish or "handling everyone like their fragile little flowers made of blown glass." In fact, that's not true at all. There is a spectrum of how you can treat people, from insulting them to being their yes-men. I am not advocating being a yes-man to suicidal people, as you seem to be implying; I am advocating sympathy instead of insults, and an acknowledgment from those trying to help that in most cases this is not coming from a place of rationality, so insulting the person by telling them how selfish their act is in your eyes is not going to make them make a rational decision to be less selfish and live in a world that they're so hurt by.
I empathize with your experience of suicide; it has also touched my life. I'm going to repeat what I said right up at the top; you said that you would never tell a suicidal person that they were being selfish, but you clearly said this in a public forum where anyone can read, and considering how many people think about committing suicide, there's a good chance someone who is will read it. It's unwise to ignore the social ramifications of your attitude towards suicide; even if you don't say it directly to the people as they tell you, telling other people spreads that attitude, and your actions can't hide that you think so negatively of that person and their decision. And even if your actions could hide it because you've spent years at acting school or some such reason, you are actively trying to spread this belief to other people by arguing about it online, people that don't have your kind of self-masking and those that believe that if you think something you should say it out of honesty. Ignoring the social ramifications of calling suicide selfish publicly is reckless and disregards how society works. It's like making sterotypical racist jokes and thinking it's fine because there's no one around hurt by it; it still has consequences beyond someone being hurt that exact moment. And that analogy is imperfect in itself because we're not in a closed room, you're screaming to thousands of people that suicide is selfish while claiming you would never tell someone thinking about committing suicide that.