The belief-action connection is like the mind-body connection in that not only is it obvious, it's so obvious that it requires quite a bit of make-believe to pretend it's not.
In your protest at not being invited to take part in an interfaith memorial for the victims of the Boston Marathon bombing, you claim:
"Including the nonreligious in interfaith ceremonies doesn't have any negative impact on religious communities"
But of course it does affect communities who believe they have a sacred duty to convert the entire world. (For the good of the eternal souls of the entire world, of course.)
"any more than allowing gay marriage has a negative impact on straight marriage"
Clearly, some people think it is their business what ALL consenting adults do in private, and who wants whom as a mate and partner.
These and many other beliefs encompassing what all of humanity should and shouldn't do have been an integral part of Christianity throughout its history, and we all know it, although well-meaning people such as yourself often stick your heads in the sand and do your utmost to ignore the obvious.
"We would never ask you to change your beliefs. We would never want you to change who you are."
You need to make up your mind. You ARE asking people to change their beliefs. (Or to act as if they believed differently, which really amounts to the same thing, since all we can see are people's actions.) And there's nothing wrong with such a request when the beliefs are tyrannical. Obviously, not all religious believers wanted you excluded from that memorial service, because things have changed a lot already. Things including beliefs.
It's just a very unpleasant and awkward (and completely obvious) fact that there are all sorts of direct and important relationships between beliefs and actions. Many religious beliefs which you are constantly at such strenuous pains to respect do not call for respect for you or me or many other non-believers. They don't even call for respect for different kinds of believers. Yes, many Christians are very respectful of you and me. They have strayed very far from the original Christian path. (For once the fundies and literalists are right about something.) And they need to stray farther, if we non-believers are going to be accorded full rights and full respect. And that's not going to happen without them confronting the full reality of Christian history. And it's simply not possible that that confrontation will not be unpleasant and traumatic for many people.
I'm sure you hear the following all the time from atheists, and I'm sure you disagree with it, but I don't want to leave you with any doubt at all about where I stand: I don't feel that you represent me at all. You are much too nice to believers for that. In fact, you're so exaggeratedly nice to them and so critical of us atheists who supposedly are "militant" that half the time it's difficult to tell that you are not a believer. I didn't enjoy saying that. I don't relish saying unpleasant things to you or to believers (or to other so-called "militant" atheists -- I think "outspoken" is a more accurate term -- when I believe they're talking nonsense, and believe me, that happens often enough). I say them because I think it's important to do so.
Wishing you and yours all the best,
The Wrong Monkey