Self-sacrifice, greater good and unselfishness

"Saving humanity/for the greater good/for the human race" is the most overrated reason ever to justify anything. For some people that stuff doesn't matter that much, for others it does. So it's a case of one person's values vs other person's/people's values. His/her selfish reason vs other person's/people's selfish reason. Of course other people can be all self-righteous about it since they're not the ones losing something important to them. They're not the ones giving up on something that makes their life worth living. Who gets to decide what's important and what's worth living for and what sacrifices other's should make for someone else's greater good?

And before Spock comes online and comments "Logic clearly dictates that the needs of the many outweigh the needs of the few." I'll counter it by saying "So quantity over quality is better then?" Things aren't valuable because they are overabundant, they are valuable because they number only a few or are unique.

I don't get the sacrifice thing at all, if we are to sacrifice the things that make life worth living, then why do we sacrifice at all, what's the benefit? To what end? As an example: if a scientist does horrible experiments on people or on animals when trying to make a "humanity"saving cure, then what is this "humanity" he is trying to save and preserve? I don't think that is a noble/worthy/humane cause, if nobility/worthiness/humanity are the first things that get thrown under the bus in order to further the cause. What are the values passed on, if they are sold along the way? What is there left of humanity except a lie of it? You don't keep humanity going by selling it away.

It's like a castle built on a swamp, no matter how fancy the structure is, it doesn't matter if the foundation is rotten. The people accepting the aforementioned scientist's actions are doing it out of selfishness, because they, their way of living or their genetic legacy benefits from it. They are valuing this concept of human species over an individual's happiness, and since human species is made out of individuals, then who gets to benefit and who should sacrifice for others? So it's selfishness against selfishness. And if the self-sacrifice is something a person values so greatly, then that person him-/herself should be one doing it, and not guilt trip/shame others to do it for him/her. *If it's SO important, you do it.* Don't expect others to go along or do it for you.

Also if a sacrificial action benefits the human race, but isn't a beneficial to the person making that action, then isn't that person by definition excluded from the human race? To clarify: An action benefits the human race, Bob isn't benefiting from it, then he is not part of the group that benefits i.e. the human race. Then why on earth would that person be concerned or feel obliged to do anything for that group?

This "human race" seems like group of ever varying individuals, that just goes on forward by fucking over it's own members one at a time and leaving them behind. No one realizes this and defends it due to the own group bias until to the point when it's their turn to be fucked over, to the point of exclusion from that group. The idea of "humans/humanity/human race" is like a fire, it needs to be fueled constantly by burning other stuff for it to justify its existence, if there's nothing to burn (no one to fuck over) it dies, it can't exist without an external sacrifice. But it can't go on forever either, because it isn't self sufficient and it doesn't reciprocate, it'll eventually run out of things to burn.

tl;dr: why should you give up the things that make life worth living to make other people's life worth living? Why are they and their values held higher than yours? "Why should I be unselfish, what's in it for me?"

PS. Also if self-sacrifice is the game and a core value of the human race, then why don't the rest of the human race sacrifice themselves for that one person, I mean isn't that selfish not to?