The generalization only works if it's weak enough to be meaningless. Thus, the generalization is bad. Examples don't make it useful.
"People act to their own benefit" is an empty generalization that adds no useful information by itself and free of context like that only serves to mislead people. It's only true if "benefit" is explicitly undefined, and only useful if you contextualize it to an specific action and benefit that you can empirically determine it's validity, like in the article.
> I also didn't say anything about pro/antisocial people
The article, and the entire discussion is about pro/antisocial behavior.