There's a 'should' either stated or implied.
Some confusion in that:
In economics “Normative Econ” often means axiom based approach. State “reasonable conditions on preferences and production functions” derive necessary implications. See… most of books like Mas Colell et al.
In common parlance, maybe in psych, I’ve hear “normative behaviour” used to mean something like “typical, normal, socially acceptable behaviour”
I don't think there's a perfect answer, but as a heuristic I defer to the logical positivists - if you can't even in principle find direct evidence for or against the statement by observing the physical world and you can't mathematically prove it, and on top of that it sounds like a statement about behaviour or action, then you're probably in normland.
That's true, but that comment was only meant for you, who seemed confused about what kind of 'should' you should use in a normative sentence. I took for granted that you already knew 'normative', because you had posted a nice and useful answer to the original question.