Ever since Richard Dawkins gave us his 7-point scale of God belief in The God Delusion, and positioned himself just shy of the strong atheist position, I have sensed a sort of orthodoxy develop around the defense to the accusations that atheists are arrogant and rely on faith just as much as believers. The common reply has been to cry foul ("atheism is merely a lack of belief in gods") and retreat into agnosticism ("I can't know with certainty there are no gods, I just find it highly improbable"). Perhaps this chicken patootie defensive response has been around a lot longer, but my impression is that it has become much more common recently.
There might be some social benefit to allowing believers to take over the conversation, since offending people can sometimes destroy relationships or even cause violence. Also, most people consider themselves good and want to be seen that way by others, so being called arrogant and irrational is bound to provoke a response (especially since -- at least in my experience -- most atheists pride themselves on being open minded, self-deprecating and uber-rational)
However, as believers with any understanding of their own theology will tell you, agnosticism is a form of atheism because belief requires a leap of faith. (That is, you can split hairs all you want over "belief" versus "knowledge," but being a theist requires action, so whether you answer "no" or pretend you didn't hear the question, the result it the same.) To me it seems that agnostics want to have it both ways, and like roulette players who bet on both black and red at the same time, are wasting their own and others' time.
I'm amused when those who defend agnosticism try to ignore the fact that nobody would give a feather or fig about it if we did not live in a world in which god belief is the default position. An agnostic will say, "I also don't know for certain if Santa Claus or leprechauns exist." Yes, you do. If an adult told you he believes in an actual Santa Claus who lives at the North Pole, etc., real leprechauns hiding gold at the ends of rainbows, you would have no trouble diagnosing him as insane. There might be a small, lonely teenager part of your brain that can't get enough mental masturbation and therefore obsesses over the possibility that maybe in some fashion there might be some sliver of a possibility that Mr. Barking Lunatic is actually correct, but the mature part of your brain would throw the door open and tell it to knock it off.
Isn't the whole point of the Flying Spaghetti Monster and Bertrand Russell's teapots to make us see that belief in God or gods is a mental illness? I see no justification to allowing for the possibility of gods, or invisible pink unicorns, or talking snowmen.
My answers to the accusations are to point out that believing you are right is not the same thing as being arrogant. If that were true, everyone with a point of view would be arrogant and the word would have no meaning. I'm careful not to tell you what to believe or to claim that I am superior to you because of it, so in no sense could my atheism be considered arrogant.
Regarding the "faith" that atheists supposedly have, I say that it's due to one of the unfortunate limitations of the language -- like the way "right" is the opposite both of "left" and of "wrong." Atheists have faith in evidence and rational thinking because they work. Sure, the scientific method leads to the wrong conclusions sometimes, but that's a result of poor evidence or poor reasoning, not the method itself. The faith of believers comes in spite of evidence, and with plenty of irrational thinking. Although you can use the word faith in both cases, they are truly opposites.