The two individualists here will basically argue about nothing until they die of exhaustion, but it could have been different. Instead of focusing on something indeterminable like the individual humors of a random group of individuals, who may have ascertain their best interest on arbitrary standards, they could have focused on the material conditions and needs that shape their lives, and they could have ascertained what was actually effecting people's decision making, instead of the empty, obvious idea that people have their own interests.
Let me just elaborate on how empty this idea is. It is a total and complete nothing that can be superimposed onto anyone at anytime. One cannot act outside of their own interests by the very definition of the popular idea of individualism. If you were to try to gamble to get rich at a billion to one odds, you are following your self-interest. If you cut your arms and legs off, you follow your own self-interest. You, by the very definition of acting, follow your own self-interest. It is a totally useless and vapid idea that only functions to allow people to cram conceptions into it, much like religion and God. It is a tool for creating "good, common sense", and a check for "good, common sense".
It is also largely without logic. It is self-justifying, and thusly never wrong. This is a bit of a repeat for why it is meaningless, and the lack of logic and meaning also makes it without substance. No matter how an individual acts, they are acting in their personal interest. Thsuly, the individualist, at any time, for any reason, can invoke their own self interest as a reason to do absolutely anything. Killing children, rape, mowing the lawn, eating grapes with biscuits, it doesnt matter. Eveything is okay because there is NO logic to it. It is just a self-interest=good, self-interest=self interest, good=good loop into infinity amd beyond. It is one of the top emptiest ideas that Zig Forums, like the rest of the world, loves and cherishes.
I pursue things just fine without looking out for my individualism, because it is literally impossible to not to act in accordance with such an empty idea. I have a new philosophy. How about groups pursue their group interest? How about, gravity pursues its physical interests, huh? You liking these, Zig Forums scholars? I have more, dont worry.
But, to return to the topic. You dont need the empty idea of individualism, when you can actually ascertain interest using materialist concepts like Marx's class structure. Then, you can have actually interesting ideas like false conciousness, whereim someone betrays their own interests. Or, of course, you can keep your empty ideas, where sacrificing your life for someone is in your self interest because of the terribly, terribly stupid, meaningless, logic-less, and substanceless idea of Individualism