How does this invalidate the thought? It's like saying survival of the fittest isn't valid because of all the different animals that have existed.
I meant that sociological behaviour does not have "one true adage" (i.e. survival of the fittest, or whatever-else), and cannot be simply concluded that way. ("It is very difficult to conclude a simplistic view of society/sociological behaviours.")
The examples I gave were meant to show that the behaviours that one believe to be "fitting" for a certain worldview, is suddenly not "fitting" in another group.
This is due to the key concept that most students learn in Sociology 101, being in a group changes your behaviour.
Therefore to study "behaviours", if you conclude a simplistic idea, you have to define its boundary. Maybe in, say, the Napolitan culture of Italia, a certain behaviour explains a certain reasoning holds true, but to generalise that to "behaviour" (in general) is hand-waving away many complexities.
I think this is where we have different viewpoints. To me, a guiding principle that exists like "optimize for survivability" isn't something that people would actively agree to, hence to "belief" is required.
It is like saying "not everyone believes in gravity, yet it still exists"