That important difference we need to make is between a "professed" atheist and a passive one. You can _almost_ get away with being a passive atheist by playing dodge ball and keeping your mouth shut. Get into why you aren't a believer and your chances of being elected become zero. Get into why religious _belief_ is a positive detriment to 21st century adulthood and you get even less popular, even with your friends.
Bernie is a good example of the passive atheist. He adds the further distinction of not identifying particularly as culturally Jewish. Now add his socialist views and he's about as close to a godless communist as any has ever been with that many votes. But he knows how to skirt the issue because he knows we are a religious nation. Check out his quotation about how he has religious and spiritual feelings. He can't deny and no one actually ever wins at dodge ball, you're just the last person in the circle. So why is this the case?
Part of the evangelical right's disdain for Europe's democratic socialism is that these countries are largely post-Christian, humanist in orientation towards people, and indifferent to their dogma and moral evaluations. When you can be "good" without being a dogma believer you've _almost_ also escaped the last bit of coercion---the last is tribe loyalty. To deny your religion can be to reject your tribal identity; this is what we mean when we say people are "culturally X", say Jewish or Catholic or something that makes you put up a Christmas tree.
Dogma, morality, tribe are the three elements of a socialized religious identity. Notice how Republicans seek out the simplest, straightest line between the individual and the group. This is because they insist that renegade individuals or "outsiders" have no rights, no claims on the real estate. You're in or you're out. Sharing a religion is an important feature of that need but not the only one. How the individual features in this collective identity devolves usually to moral or personal regard. You think so-and-so is a "good person" because you know that person and this solves the story in most ways but not politically.
The irony in this is that the 1st Amendment freedom makes further interest in someone's religion something we don't know _how_ to talk about, it is relegated to the private. But once you are a political person, you _stand for_ the flag, for country, for _us_ and that means you have to conform. Cross even a little out of the Protestant Christian lanes and there is a lot of 'splaining to do.
The article's essential thesis is that atheism is the theists are the problem and I could not agree more. But he fails to understand more deeply I think why people don't like professed atheists. He seems to think that it hinges on our suspicions of moral inadequacy, i.e., professed atheists are immoral and then resorts to the usual disproofs. This is, of course, a false equivalency because it's a black swan problem: all you need is one deeply professed atheist who is moral and the argument fails. Meh. This is not the problem. The author has missed the real point.
Religion is inextricably woven into identity: social, cultural, and personal. All of those matters have their own histories. No matter how you privatize religious identities like Americans do in the 1st Amendment or how claim they are preempted by some claim (often religious) of our shared humanity, when someone _actively_ dissociates from religion, they are creating an antagonism against _you_ even as they formulate a new tribe, in this case the atheists.
Humans are Us-beings and no matter how we try to be _human_ beings, our Us means there is a Them. When there is a case being actively made that you and your version of Us is somehow gravely mistaken, wrong-headed, superstitious, silly, imperialist, in some way less than correct, valid, or socially legitimate there is a natural comeuppance, we take umbrage. We don't like being told that something we use somehow to formulate our identity is at best a tribal need and at worst fatuous nonsense.
In short, we _always_ take religion personally. We can't help it. And when people are affronted they feel attacked, dismissed, trivialized. It's not a moral problem as such, it's a matter of getting into the fiber of being and that _feels_ like a moral provocation. The professing atheist is making claims about our fragile and precarious hold on meaning, which we become desperate and angry about because we don't like to be told how touchy, insecure, and contingent those feelings and ideas are.
Enter modernity: we are daily undermined by diverse views, new facts, and global dangers. We may need an atheist to deal with those facts because Team Magical Friend always makes matters worse. But that will have to be a passive atheist, one who makes us _feel_ like our personal identities are being unthreatened, especially by the facts.