I think, when atheists say a child is born an atheist, they mean that the child has no innate beliefs or religion. If a child is born and raised without religion or theism, most likely they would not develop such a strong faith. We can see this in those parts of the world with very secular populations; the people are not all that religious (outwardly, anyway).
It irritates me too that a theist is automatically less intelligent than an atheist, to most atheists. I think this is because it doesn't matter how smart the theist actually is, the atheist believes that because the theist can accept\believe in\have faith in something that the atheist believes is crap, it automatically means there is something wrong with the way the theist thinks. Like, their thoughts can't be 100% coherent, because there is a loose wire in there that allows them to have a belief that is not "true" (according to an atheist).
A few years ago I went through quite a strong atheist period. I read The God Delusion by Richard Dawkins, and it was apparent to me that he is not much better than an outspoken theist, as he uses the same technique of taking passages out of context to prove a point. I was very disappointed when Dawkins reduced himself to that, and in my eyes his credibility went out the window.
But I suppose where Dawkins is concerned, we need to remember the environment he has been in for his life, raised in and surrounded by strong Christian theology. It is natural that he's developed a venom against is.
My partner is an atheist and listens to a lot of atheist podcasts, so I get to hear all the arguments. My favourite, actually, is The Atheist Experience. It's pretty entertaining to listen to them argue. It can be challenging at times, though, when the atheists throw away all validity of feeling. I want to ask them why they act on feelings they have, such as love, yet for a spiritual person to act on their feeling of spirituality, it suddenly becomes invalid.
Sikhs are panentheistic; it is much easier for an atheist to argue against monotheists because the monotheistic Gods are usually quite colourful characters whose followers have strong mythology around what their God says, and things their God has done. Sikhi doesn't have this mythological God-character, so it's harder to attack. Dawkins calls pantheism "sexed up atheist", and other atheists ask why pantheists/panentheists are so desperate to apply the word "God" to what is otherwise known as the "universe".
At the same time, atheists have some measure of a point when it comes to advocating for a secular society. I wholeheartedly agree with them, and oftentimes they will say they don't really care what individuals believe, but the problem comes when they try to make other people believe it, or bring it into education and government, where it doesn't belong. And it is indeed a particular problem in America, where fundamentalist Christians do try to teach creationism to children in school, etc. I wouldn't like my child to be taught young earth creationism in science class, that's for sure. I don't want my child to have to chant the Lord's Prayer every day.