There's nothing wrong with proselytizing per se. Everyone proselytizes. Even Coren is proselytizing. Every conversation, essay, comment intended to persuade the listener to the speaker's point of view is proselytization. Proselytization is a normal, ordinary, prosaic activity, part of the ordinary human experience.
The Gnu Atheists do not condemn any religion because they proselytize. Sure, there are issues of appropriate time and place. Some people find it irritating to have strangers knock on their door early Sunday morning. Fred Phelps is quite rude to protest at the funerals of soldiers. There are some exceptions, perhaps — atheists don't maintain a rigid, tightly disciplined organization — but the Gnuiest of the Gnu Atheists typically adhere to ordinary social standards of appropriateness... so long as those standards are generally applicable. But, by and large, there's nothing wrong with telling people what you believe and doing your best to persuade them to agree. The Gnu Atheists do not object that the religious proselytize their views, we object to the views being proselytized.
Proselytization by itself does have one important social consequence: If you proselytize your opinions, you implicitly open yourself to criticism of the content of those opinions. The same is true for both religion and atheism. Yes, we proselytize, and yes, the content of our views is thus open to criticism. Bring it on! But by the same token, by proselytizing their views, the religious equally open the content of their infantile fantasies to criticism. I don't demand that anyone shut up, but if you want to shield their content from criticism you have to keep your views to yourself, socially and individually. If you want privacy, you have to exercise discretion; if you don't want me to comment on the length of your penis, you have to keep your pants on.
No one, not even the most virulent and vitriolic fundamentalist, should be criticized for proselytizing. Much as we'd like to tell people to just shut the fuck up when we find their views obnoxious, deplorable or despicable, that's not a realistic option. We are actually better off having more views openly aired, even those views we find reprehensible. To the extent that people do in fact tell others to "shut the fuck up," we should see this construction as idiomatic for, "I think your opinion is egregiously stupid or evil. I'll give you a chance to avoid social awkwardness by pretending I didn't hear what you just said. If you say it again, I'm going to comment on the content of your view, which might cause you discomfort or embarrassment. Your call."
Religions proselytize. Their content is thus open to criticism, and we Gnu Atheists do indeed criticize the content of religion: Religion is infantile, socially and politically damaging, and it's not true. If you want to respond to the substance of this critique, knock yourself out. If you don't want to hear this critique, you have the option of keeping your opinion to yourself. Take your religion out of the government, out of public life, out of social life, and no one can legitimately criticize your religious beliefs. You don't have to do so, you're free to put your religion anywhere public you please, but then you invite the concomitant criticism and evaluation.
Yes, the Gnu Atheists proselytize, and we're damn proud of it. We're not going to sit down and shut up. Like everyone else in the world, we have opinions, we believe them to be true, and we try — using legal, peaceful and appropriate means — to persuade others that we are indeed correct. That's called living in a society. If you want to criticize what say, have at it. Fight clean or fight dirty; we're not afraid. But fuck you, Ms. Coren, and fuck you to anyone else who says or implies that atheists are fanatics or "fundamentalists" just because we believe what we say and we say what we believe.