Ok then, Einstein, since you clearly are the authority on the subject, why don't you show us some EMPIRICAL evidence that all acts of altruism are selfish. We can piss at each other all day about who understands the concept better, but the meat of the matter is that you have made a claim of empirical verifiability that you have yet to support.
I do not understand why you are unable to recognize the empirical evidence of self-interest that is clearly contained within my soldier scenario. Alright then (taking a deep breath), I will be congenial and considerate in describing another view for you.
You are going to be a third party viewing this unfolding event. Since you used the scenario of helping an elderly lady across an intersection, let's use that descriptive analogy.
As you were sipping your Latte from under the umbrella at the outdoor court of your favorite coffeehouse, you noticed an elderly lady and a middle-aged gentlemen standing near the northwest corner of the major intersection( the coffeehouse is on the southeast corner). As soon as the "WALK" sign illuminated, the elderly lady stepped off the curb, but immediately stumbled as she tried to plant her right foot on the asphalt. Our middle-aged gentlemen quickly evaluated the situation and wanted to help, by stabilizing the wobbly lady with a quick grasp of her left arm. He then continued to help support the elderly lady as she walked across the entire intersection, and up onto the sidewalk.
Now, the sequence of self-interest indicates that the giver(primary transaction) of the potential benefit to another individual, must make a decided decision to engage OR IT SIMPLY WILL NOT HAPPEN, and this is the empirical face(evidence) of satisfying SELF-INTEREST, BEFORE the recipient of the benefit(secondary transaction) could possibly receive this empirically based and measurable benefit. So, as the elderly lady stumbled, our gentleman thrusted out this arm (empirical evidence of self-interest) to grasp and steady the elderly lady as they continued to walk across the intersection. The gentleman satisfied his self-interest, because he decided to intervene, and we know he wanted to intervene, because of the MOUNTAIN OF EMPIRICAL EVIDENCE that was available for you to view and measure as you finished your morning Latte.