Have you ever seen Christian bumper stickers that says something like "not perfect, just saved"? I suppose the owner imagines that this is an expression of humility for admitting that one isn't perfect, but the attempted humility fails because of the smug expression of superiority: "even if I'm not perfect, I'm still going to spend eternity in paradise while the rest of you losers will suffer an eternity of torment. So there!" Yet, it's atheists who are accused of being arrogant.
Some religious theists like to complain that atheists are increasingly arrogant towards religion and theism, but there is little conscious recognition of how arrogant religious theists themselves can be. This arrogance seems to stem from the belief that one is not only in possession of the Truth, but of a divinely provided Truth — these religious theists know the Truth and are convinced that part of their job is to help poor, deluded atheists find God's love for them.
Granted, everyone can be like this when they think they are right — even atheists — but there is a difference between simply thinking that you're right while others are mistaken and thinking that you possess an unmistakable, divinely provided truth such that others are willfully disobedient, in denial, or in league with Satan. Even the most arrogant possessor of a mundane truth about the natural world pales in comparison to a self-righteous religious believer convinced that they not only know the Will of God, but that everyone else would as well if they were only equally good and righteous.
In the process of such thinking, religious theists develop a tendency to make all sorts of arrogant assumptions about atheists, what atheists think, why they are atheists, and how best to approach atheists. Instead of asking questions and considering that they have good reasons for disbelieving in gods, atheists are treated as objects for evangelization whose own perspectives are unworthy of being heard.
Some believers don't seem to give any thought to the concerns of others:; their way is The Only Way, and even people who do not accept it are necessarily ruled by it, whether they like it or not. If they don't think that they are, then it is simply because they fail to acknowledge the existence or the sovereignty of the One True God. It's amazing that religious theists can accuse atheists of being "arrogant" even while having tolerated far more extreme arrogance in their own ranks for decades — if not millennia.