This is the essence of the cuck mindset right here.
I am not a psychologist...but I am not sure that you are correct...not am I sure that you are not. Just from what I have seen in my own experiences...these guys with their own "huge cocks"...who have spent years, decades, their entire life, having sex with women...married/single...from other marriages and relationships, and their own wife/gf just accepting it as because they know they can not realistically "stop" other women from making a pass at their huge cocked husband and/or their seeking out the other women....those guys with the "huge cock" react in different ways when they realize that someone is not only larger than they are, but extremely much larger and more virile than they are....some get almost "neutered" in that they lose erections and/or simply can not get it up no matter how much other women "help them"...those are a few. Others, usually the "biggest" of the "huge" sometimes get even harder and are in shock, but also "fascinated'...(I am not sure that is the right word, but it does come to my mind) and stare and are curious just like others....and often they are not so much about their wife now fucking another guy with an even much bigger cock than their own, but they are fascinated to watch the cock and see their wife, who is accustomed to their "huge cock", struggle with someone much larger and more virile.
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As I have heard variations of it so many times during and after sex with their wives..."that was incredible", "better than any porn movie I have ever seen", "I never saw so much cum", etc, etc, etc.
The thing is...one that is almost always consistent...is the wife/gf...after our having sex...almost always want their husband to immediately have sex with them and have their husband feel how stretched out they are and their pussy filled with another mans cum.
And I have also never seen a guy last more than a minute after pushing inside their wife/gf after I pulled out of their now stretched pussy...never. Most guys last just a few moments or few strokes, they are so sexually excited. And they all seem to have their own big orgasm they are so excited. And the women, sometimes they cum too from their "huge" husbands orgasm turned them on..and some do not at all...they just watch and feel their husband lose control and orgasm while they seem to be feeling "nothing" sexual.
The dynamics and relationships within couples....you just never know...until everyone is in their birthday suit and the "huge" husband is not the "king cock" any longer.