No, because in the case of atheists, it might simply be a disagreement
You don't spend a significant amount of time on a religious forum if you "simply" disagree with their views. We don't seek out people who we simply disagree with, just to tell them that we disagree.
It may be that the only threat that religion (any or all of the many competing religions) might be thought to pose is not one of casting into doubt an atheist's (or other nonreligious person's) worldview, but rather the threat of (or tendency toward) imposing an authoritarian view of reality and control of society and individual freedom, which is antithetical to the health and wellbeing of a diverse society, and anathema to many of its members.
While this could very well be the concern, that doesn't mean it's a rational one. Religious beliefs pose virtually zero threat to western society today; if we need to be afraid of any ideologies, it's political ideologies. Politics are the new extremism, the new fundamentalism.
Interesting how this has coincided with the reduction in religious affiliation among people. It's seem as though we may be religious by nature, and we need to dedicate ourselves to something religiously, so people have simply replaced actual religion with politics.
But I digress; the point is that a fear of some sort of authoritarian theocracy is irrational in the modern western world, as is believing that arguing with a few religious people in some forum would have any effect whatsoever on the possible likelihood of such a thing happening.