I agree with most of this. The less often it is used does make it feel more unnatural than if it were common, but even human speech, as it is now, has profanity seem natural.
For example, let us say a bomber is talking to his victim on the phone and says, "There's a freaking bomb on the bike" (This is an actual example, with some possible differences). To me, this feels unnatural, because this is something the person on the bike would say, not a bomber, especially if there was no mention of a bomb before.