The headline "Ever Meet a Happy Atheist?" go my attention, because I do know happy atheists. And the article quite reasonably points out that there are many non-Christians who have no objection whatever to the celebration of Christmas, including religious symbols. It's the militant atheists, together with such organizations as the ACLU and Americans United (both of which no doubt have some atheist members, but also members of many religions including Christianity [though it's a curious form of Christianity which argues against any public celebration of faith]), who are the villains in this case.
Too bad. Most atheist will never read it, just figuring the headline’s representative of the article.
I think he expanded on this point a bit, talking about how atheists are generally unfulfilled people. It's a bit more than that, but that's the idea. Atheists are not fulfilled people.
Like the old saying goes, if you don't stand for something, you'll fall for anything.
Not everyone is a zealot, but everyone that's ever been exposed to the conflicts of real life winds up believing in something. Eventually, some atheists will settle into causes that they use in place of spiritual belief. For instance, the ACLU or science. Others just don't think about it.
Well rounded atheists are like famous moderate leaders in history. They just don't exist. Every atheist I have ever known, regardless of temperment, seems to lack some element of the human dynamic. I suspect this is the authors point.