For me, the falsity and harmfulness of the claims trumps the genuineness and significance of the experiences, if the latter is dependent on the former (but it doesn't seem in principle like it should be).

I agree with the first part of your statement, and as for the second -- yes, exactly. I don't think the experiences are dependent on the claims. In fact I wouldn't be surprised if the claims [regarding the existence of a god or gods] originated as a rationalization of the experiences [the particular chemical state that produces, in human brains, a sense of ecstatic spiritual awareness].

And to me it makes the atheist message stronger if we can still have our tight-knit social communities and our occasional ecstactic brain-state, even while we agree that there's almost certainly no such thing as God.