In other words, they should be especially militant, given your hypothesis. They are not. I suspect you know why they're not.
I don't know who you think is disagreeing with you that "religion is not essential." Who in the world argued it is? As a matter of fact, I pointed out that with Stalin and Hitler, their belief that no higher power would hold them accountable made them more likely to continue with their "improvements" of mankind.
You cite a list of individuals. With the possible exception of McVeigh, were part of a larger terrorist movement. We had no one who followed any of those individuals. We see Islamic terrorist attacks followed by Islamic terrorist attacks because there is something unique about Islam that isn't present in Christianity or Judaism or Buddhism or Hinduism or Sikhism, et cetera.
Finally, your estimates of how many Muslims actually disagree with the "death to apostates" principle is undoubtedly lowballing it. I'll try and dig up the polling on that. As Sam Harris has stated quite well, the jihadists give a quite plausible interpretation of Islamic texts. In contrast, no one believes that the Gospels give license for Christians to commit terrorist acts.