Do you personally believe that every atheist or non-monotheist is doing so out of rebelliousness or stubbornness? Does this really seem plausible to you?
"If that's the idea", well, then it is pretty obviously incorrect. An omniscient God would know as much.
As for myself, I was pretty devastated when I lost my faith in the existence of God. It was heartbreaking. I tried to regain it, but could not. It had nothing to do with my ego, but everything to do with the inability to believe something for which there was no adequate evidence.
Perhaps the issue is that your idea of "Evidence" is based on something you place undue faith in. You think the solar system and the life system within the Earth can result as a matter of chance, and I believe that is something the "Fool" who "Says there is no god" would believe.
But this goes back to the age-long attempt to ask Atheists to define what kind of "Evidence" they'd accept for the idea of a Creator. It usually ends up getting nowhere asking for such an example.
So yes, saying there is "no evidence" for a god, in my opinion at least, is an act of rebelliousness, of which a full philosophical explanation would be beyond the scope of this thread.
The God of the Jewish people (as recorded in the Tanakh), the Christian God, and the Muslim God all seem to be pretty clear that they, and they alone, must be worshiped.
By the Israelites according to the Torah, and those living within their borders. This is a difficult subject also best fit for another thread.
Worshiping any god, even polytheistic ones, would be evidence of a humbleness of spirit, dontcha think? So, if saving us from our egos is the reason behind God's demand for worship, then wouldn't worshiping anything but ourselves serve that purpose? That doesn't seem to be how God feels about it.
Part of why I believe the gentile nations were meant to bow before the regional archon.
Ignorance, or inability to understand, is not the same thing as a bloated ego, and could just as easily account for this.
"Inability" to understand? What makes one unable to understand the idea that the life we experience would necessitate a creator? Rather, it would take an extreme amount of understanding astronomical theory to even believe the possibility that the solar system could fit together without a creator, and those theories are filled with holes. I see it as a willful, stubborn rebellion, regardless of how its dressed up as, and I believe that's also the Jewish position in the Talmud, but I cannot say for sure.
Methods of worship are largely culturally based. You absorb, as a child, how one is supposed to worship. If you are born into a culture in which physical signs of worship are not performed or are not emphasized, then that is likely how you will worship too. Again, nothing to do with ego.
I believe every culture worldwide has had a concept of bowing and sacrificing. From the Americas to the Asians and the Africans in between.
For instance, Muslims believe in prostration for prayer. Catholics often will kneel. Most Protestants will simply close their eyes and fold their hands. Is one being more pious than the other? Are the Protestants and Catholics being more egotistical than the Muslims for not knowing they should be prostrate?
Kneeling and prostrating are both methods nonetheless, whether one is more correct or not is a minor detail, the fact is that they are displaying a physical sign of submission. I DO Believe that there is something to arrogance and ego in the Protestant belief even beyond that of the Orthodox church but that's an entirely different subject best for another thread.
If someone believes in a Creator-God but does not believe that this God desires worship, how is that egotistical? Think of the deists, for instance.
The idea that the Creator would just walk away and not want a sign of submission from its creation in the Deist method, is in my opinion, a form of lack of humility and wanting to be free from the Master.
Notice too, how you worded your response above: "This could be seen as a sin of haughtiness..." I do not doubt that some people could perceive it in such a way, but it does not follow that their perception is an accurate depiction of reality.
Everyone is working with perception. This is basically an attempt to make an assertion upon an age long question of Epistmyology of personal reality versus Empirical objective reality.
How so? You asked, "Why would anyone refuse to bow down and show a physical sign of allegiance to the Grand Overlord and Overseer of Cosmic Justice?"
There may be reasons, but I believe each of those reasons is based on something we will be judged by which have an objective ruling to answer to.
It is a valid response, then, to point out that "bowing down" and "physical signs of allegience" are not the sole forms of worship, or expressions of submission to a higher power.
Throughout history, there are few if any ways of showing "Worship" (and the meaning of such in ancient languages is purely to bow down physically), the concept of this changing is extremely recent. Do you see how that applies?