In the movie: The Fifth Element, when the Mondoshawans made their appearance I thought to myself 'Those are the largest Tardigrades, that I've ever imagined'
And your Molyneux, argument introduces many valid points.
It could also be further distilled down to simply fear of the 'other' or quite simply fear, as a base emotion. Fear, is a great motivator for many of the lifeforms on this planet. Fear, triggers the self preservation instinct, and ego can also be successfully argued to be the prime motivators for humans.
The Fermi, paradox is also a very valid argument. Even if only for the purpose of provoking more thought.
https://www.seti.org/seti-institute/project/details/zookeepers-alien-visitors-or-simple-life
Also, I do not feel that the religious, or other cultural values, norms or concepts would be shattered beyond repair. Quite the opposite may also occur. This is also a possibility, is it not?
I have personally witnessed events, that produced unexpected results.
This sort of assumption that Mankind's psyche, and institutions would implode are not based on even recent historical outcomes.
How did the wonder, discovery and implementation of Electricity, effect Mankind's psyche, or social/religious etc; institutions?
How did that knowledge and technology effect the human condition?
Did it usher in a Utopian shift? Shatter long held beliefs?
I am of the opinion, that direct contact with other, and especially with more advanced civilizations would most likely follow this model.
The fact that we have had the Nuclear and Biological, capabilities to self destruct for several decades has not come to pass.
Does provides a glimmer of hope. And here we may also call on that curious emotion of faith.