The ethics of breaking belief

I’m not sure if this is precisely the correct forum for this, but if there is a better place, I don’t know what it would be. At any rate...

I’m a student a Catholic university, and there are (as one might surmise) quite a lot of Catholics here, along with assorted other theists (yes, even some in the biology faculty). For this reason, I find myself acquiring more and more devoutly Catholic friends, and some of them I have grown quite close to. But the God issue keeps coming up for one reason or another, which is a source of tension. And yet as I grow closer to these people, it becomes clearer and clearer that each theist has a certain personal sequence of Dark Arts-ish levers in eir head, the flipping (or un-flipping) of which would snap em out of faith.

So the question is this: in what situations (if any) is it ethical to push such buttons? We often say, here, that that which can be destroyed by the truth should be, but these are people who have built their lives around faith, people for whom the Church is their social support group. If it were possible to disillusion the whole world all at once, that’d be one thing—but in this case my options are limited to changing the minds of only the specific individuals I have spent time getting to know, and the direct result would be their alienation from the entire community in which they’ve been raised.

And yet it is the truth.

I’m conflicted. LessWrong, what is your opinion?