I read so often from liberal theists, faitheists and people who want to frame science, that "aggressive" atheism is "hurting the cause" of atheism or reason or cute puppies, that it will convince nobody and turn off those we wish to convince.
These arguments are long on emotion and very short on evidence. They're also factually inaccurate (in that most so-called "aggressive" atheism is anything but aggressive).
My usual argument has been that not every atheist activity is about convincing others; in fact, hardly any of it, as far as I can see.
My life is not a marketing exercise.
But sometimes it actually does impact those we criticize, and sometimes they come to understand what we're getting at, whether that was the aim or not.
I have read a lot of deconversion stories and related discussion (hundreds by now).
I have seen many times former theists say things along the lines of "Well, actually, I had my faith criticized and it wasn't until that moment that I began to really think about my beliefs."
I've seen comments like that on blogs, in forums, on youtube, yahoo answers and reddit. I saw another only this morning.
Not every deconversion of course - a lot of the time people start thinking about these things themselves, or the trigger to start down that road is something different. But quite a lot of the time, an aggressive challenge to someone's beliefs is actually effective in getting them to think about it. Yes, it will also annoy plenty of people - people don't like having cherished beliefs criticized. You have to pick your moments. But that doesn't mean it is automatically counterproductive.
Being likeable is not often a catalyst for change.
I think being generally thought of as likeable is impossible. Atheists - unless we hide ourselves in a closet forever - will often be regarded as confrontational, simply for existing.
There's absolutely a place for people like Hemant Mehta, with those who seek to actively engage with the religious. More power to him. I think Hemant and people like him do a great deal of good, not only for atheism and reason, but for wider humanity. There's also a place for the louder, less compromising voices.
I have never once seen someone say "my former beliefs were respected and treated with deference - and that was what convinced me they were wrong".
Why would it? How could it?
Yes, if you want to work with theist allies in some other cause, be it gay marriage or proper health care or whatever, it might not be the occasion to critically discuss the truth of their beliefs, but to focus on the current priority. (On the other hand, it's probably never the time to agree to propositions you acually disagree with, or even to hold silent on them, simply for the sake of getting on.)
I think most atheists can manage the distinction between present priorities and longer term goals well enough.
But if we're talking about reason and evidence and skepticism, attempting to promote them and spread them, it makes no sense at all to ignore the most egregious transgressions against them.
If we are trying to get people to critically examine their beliefs, it makes no sense to pat them on the head and tell them we think their crazy beliefs are just dandy. Freedom of belief is only that - to believe as you like. It doesn't mean freedom never to be called on those beliefs. It is not freedom from criticism. It is not freedom from questions.
Our commitment to freedom of belief does not mean we must accept other people's fanstasies as perfectly valid, or that we must meekly hold our tongue when they're brought up. Indeed, we should not. The person you risk offending may also be the person you eventually goad into the line of thought that leads them to convincing themselves.
What could be better than people thinking for themselves?