Selfish Altruism?

"People think just because someone is doing something altruistic that person is noble. Nonsense", I burst out.
My friend looked up with that expression that I knew so well. The one that said that, before the conversation was over, I would be feeling six nano-meters tall and crawl out vanquished. Not this time, by God, I had impeccable logic on my side.
"I'm sure you have a strong reason for saying so", he said, in a tone that indicated that he was sure of the exact opposite.
"Well, if someone is, say, feeding the poor, obviously he is doing it because it makes him happy. So, he is doing what makes him happy and I am doing what makes me happy. So what is the big difference?"
"Hmmm! So, essentially, you are saying you are as good as he is, even if what you are doing is drinking yourself silly and what he is..."
"Hey! Listen! Let us not get into what benefits society and all, here. We are only talking of whether there is any nobility in it. Just because what makes him happy happens to benefit society, HE is not being any more noble than me."
"Ah! So, by the same logic, you are as good as the chap who abducts and rapes women. He will also claim he is doing what makes him happy, just like you and, if what makes him happy happens to be to the detriment of society, by your logic, it should not matter in judging him."
I should have known! Every time I step in, armored in confidence with my reasoning, one of these chaps pokes a needle into it.
This chap was not done with me, yet.
"You seem to think that nobility means that the person who is considered noble should be unhappy doing it. Can't you understand that it is not whether he is happy or not but WHAT makes him happy which makes a person selfless or noble? Is getting rich quick your route to happiness, or creating an institution, or molding young minds - WHAT satisfies you to do defines you as a person. Whether you need to hurt others to feel happy; whether you seek only to satisfy your own desires to feel happy, even at the cost of others; whether you find happiness in giving succor to others - it is WHAT makes you happy that defines you as a person."
"Come on! If so, then why do these guys get called self-sacrificing? They are not sacrificing their happiness, are they?" I said triumphantly. There. Let us see him answer that.
"You truly belong in this digital generation. Are all choices either-or? As in, you feel happy eating your cake OR you feel happy giving it to the beggar. And, in the latter case, you have no desire at all to eat it, ONLY the desire to give it away?"
Shucks! This chap was too slippery. I should have known! I should have known! I have had enough experience of him after all.
"You do not always choose between options where you dislike one and like the other. Mostly, in life, you may like even ALL the options and still have to pick one. To pick one IS to sacrifice the others, in a lot of cases. And where one sacrifices his personal pleasures in order to benefit others, he would be considered self-sacrificing. Even if doing so also makes him happy."
Punctured again. I would have been better off keeping my opinions to myself and saying it in safe echo-chambers on Facebook.
"But then, what is the point explaining all this to you. You lack the equipment to understand - Brains."
"Say, why do you keep insulting me..." I whined.
"Because, on occasions like this, it makes me happy."