In my opinion, I don't think it's outlandish to see suicide as selfish, but only as long as you consider the fact that everyone is inherently at least a bit selfish by default. "Looking out for number one," so to speak, is the brain's main goal in order to promote its own survival. For those who are suffering, "survival" can end up presenting as suicide (though I know this sounds immensely contradicting), because that IS them "looking out for number one"... Making the suffering stop, whatever the cost, even if they DO truly care for those they leave behind. The selfishness of wanting to save oneself, however one can, doesn't negate the care they have for others; these can coexist. In the end, everyone is selfish because that's how humanity is biologically wired.
So, all of this considered, I honestly think most of the controversy of this discussion comes more from deeming "selfishness" automatically as a negative or evil thing, because personally I really don't think it is. It's just a neutral trait that comes with being any animal with SI.