It's been said that no man does evil in his own eyes. All interest is self-interest. The difference is in how we choose to see our 'self'.
The men who waded ashore on the beaches at Normandy were not acting in their self-interest. They wanted to save civilization.
If you say that they were acting in their own self-interest because they saw themselves as part of civilization then I say that's a stretch. When you say that, you can't say to a child that he is being "selfish" because all things are selfish. It makes the language clumsy to have to say, "you are not acting in the interest of the greater good".