I still pray before going to sleep, only do it as a quick evaluation of the day.
You recognize religion as a collection of metaphors. Metaphors are useful because they distill a complicated reality down into more easily grasped sound bites.
Similarly, I still attend religious ceremonies and institutions as they are good and useful means of socialisation.
The music can be exhilarating. The first songs I ever learned were Christmas carols. All through high school I sang in the choir and half of our repertoire was hymns. I'm sure even the sermons can be moving if they're not too shrill; although the only religious service I've been to that I found engaging was a bar mitzvah.
I don't question or debate all/many theists I meet, I just nod my head. Why not?
Because we'll never change their minds so there's no point in bothering. I'm fairly certain that of the handful of religionists who become atheists in a year, almost none of them were significantly influenced by their atheist friends.
Intellectually dishonest, withholding the truth, improper? No, its just practical and useful.
I think that being passive and not arguing with people with whom we disagree is not a form of intellectual dishonesty. I suppose allowing them to believe that we agree with them could be construed as such... But I live in a country in which the majority of the population are religionists who automatically assume that every other self-respecting American is too. I don't have the time or energy to let every one of them know they're wrong.
So what is your plan for times of need and distress? Suppose you have a car accident, are seriously injured, and your theistic friends come to comfort you. Already seriously injured and in distress, do you believe you can keep up the pretense of being a theist while not actually being one?
If these people are the good Christians (or Muslims or Rastafarians or whatever) they claim to be, they're not going to start preaching to you while you're lying on the road in pain. This is not the time they'll pick to ask you earnestly if you really believe in Jesus Christ (or Mohammed or Ras Tafari or whatever).
What if in times of your greatest need and distress, you get discovered, outed - and abandoned?
All of these religions teach their followers to be charitable, even to unbelievers. In fact especially to unbelievers, because being kind to someone and attributing the kindness to one's religion is the absolute best possible way to evangelize that religion. Churches and other places of worship are full of people who haven't exactly come around to believing in the dogma (if they even understand it yet), but will be forever loyal because of some kindness they received when they were hopeless.
So if these are good people, they're not going to pick
right now to jump on you for not being one of them.
Nonetheless, this is a good example of why you should be truthful with your friends. Not to tell them that their religion is bullshit and try to talk them out of it, but merely to let them know that you're not a member. Friendship is supposed to include honesty, after all! If you can't tell your friend about something as important as your religious or non-religious views, then one of you isn't really a very good friend.
Or suppose a theistic friend of your gets seriously injured - and he asks you to pray for him, or to lead group prayers for him?
Another good reason that he should already know that you can't do that--not because you're unkind, but because
you don't know how. I'll bow my head and say something kind, or be respectful if another person leads the prayer. There's no reason to be
disrespectful of someone in their time of need.
If I can sing carols to Baby Jesus in the Manger, learn three different versions of "Ave Maria," absentmindedly say "bless you" when somebody sneezes or "Goddamn you" when they cut me off in traffic, and put up a fabulous Christmas tree (with my wife who was raised Jewish but is now a Buddhist), I'm hardly going to turn into a militant, evangelical atheist at a moment when a friend (or even a stranger: "we're all in this together") needs comfort rather than a sermon.
Besides, hopefully we all know that prayer, and spirituality in general, releases endorphins and might make the difference between a victim living and dying. As I've pointed out many times, Jung's work with archetypes argues for a human brain architecture that is genetically predisposed for supernaturalism.
I doubt that your theistic friends, acquaintances, relatives and colleagues would look kindly on this charade of yours. Once they find out, they may feel you have betrayed them.
There are communities, even entire countries, where to admit being an atheist would be dangerous. But those people are probably not posting in this discussion.
They may even appreciate you more if you simply made clear you're not a believer, and may be willing to stay on friendly terms with you.
Especially if you're not militant. Many of us, perhaps most notoriously yours truly, work up a good head of steam in our hateful comments about religion here on SciForums. It stands as a bulwark against science; averaged over time it has done far more harm than good, yatta yatta. But we're sitting here in an informal academy of science and scholarship, a proper place for that kind of talk.
But as the only atheist sitting around the dinner table with your religious friends, well that's not the proper place, unless they all came over for the express purpose of arguing religion.
The charade you're doing is setting everyone involved up for betrayal.
I think we would all like atheism and atheists to get more respect. Lying to people isn't going to make that happen.
You might be underestimating how stressful a severe injury is. It might disable you from continuing with your charade.
Especially if you start yelling, "Oh Jesus, that hurts!"