Why can't we just admit we don't know where the universe came from?
Because the unknown is frightening. It's more comfortable to assume a benevolent deity created everything as his own personal ant farm than to contemplative the prospect of an unthinking universe unconcerned with your existence.
Religion is, in many ways, the very peak of arrogance. A humanist view depicts human life as an accident, created by no one and likely unremarkable in the cosmos. If you insert God, then we're suddenly VERY IMPORTANT. We go from being the descendants of some accidental self replicating RNA to being part of the intimate design of the cosmos itself. Instead of being an offshoot of what the laws of physics happen to be we're the REASON those laws were CREATED to be the way they are.
Believing in a personal God elevates you. It makes you important instead of irrelevant. Instead of being one of the 6 or 7 BILLION creatures pretty much just like you, the most important entity in all of existence cares so deeply about you that he suffered personal agony just do you could spend eternity with him.
You can see the raw ego of religion in how the religious often describe atheists. Instead of seeing the surpassing humility of admitting "I am nothing" they convince themselves, through a grotesque parody of logic, that such an admission is somehow prideful. Insisting the universe, in all its vastness and glory, was created for you and your own kind is transmuted through this alchemical "logic" into an act of humility.
Being Christian does not preclude an honest self assessment. Pride is a major component in religion. Why do you think there are so many warnings about it in the Bible? If we are indeed the peak of creation, if intelligent life is the reason God crafted the universe, then isn't that something that can swell one's head? Doesn't that make it even MORE important for Christians, indeed most theists, to have a keen awareness of how innately arrogant our beliefs are?
Even when I was so far to the right I complained that Rush Limbaugh was a bit liberal, I saw the argument of atheism being itself arrogant to be a comically misguided thesis. Sure, you can find plenty of noteworthy atheists who are arrogant SOBs, but then most people who achieve a significant degree of fame and notoriety are equally arrogant. The problem is, theist critics assume that atheists are trying to place themselves above God, or elevate themselves to a peak position. They honestly can't understand that many atheists don't place ANYONE at a divine level. Knocking God off the pedestal does not automatically elevate everyone else.
Personally, I blame Satan. Not a literal Satan mind you, as his material existence is irrelevant here. I blame the common interpretation of scripture and tradition that depicts Satan as a rebel who sought to unseat God and take his place. This narrative has infected the human consciousness to the point where many Christians can't even contemplate atheists without seeing them as mini-Lucifers, out to unseat God and rest their own rumps upon the divine throne. They don't understand that the statement "I see no proof of God" is not even in the same ballpark as "I AM God." Knight VII's insistence upon humanism being inherently arrogant is based, in part, upon the inability to make such distinctions.
I've heard many pastors and speakers claim that atheism is inherently prideful and arrogant. I've never heard a decent explanation of WHY they believed this to be so. The most common explanation was that atheists "want to make up their own rules," an accusation that's simply not true. I suspect many of the people using that argument are themselves so morally bankrupt that the only way they can behave civilly is with the threat of a vengeful God and violent government looming over them. They falsely, and without foundation beyond their own hearts, equate the removal of God with the dissolution of morality and base their objection to atheism upon that.