It seems to me that the overwhelming majority of Calvinists are also irrational, in that their attitudes and actions contain contradictions which they make no attempt to explicitly understand or even acknowledge.

Furthermore, it is far from clear that Calvinism is compatible with rationality. If it isn't, in a hypothetical where I am Calvinist, I wouldn't be rational. I would likely do the same things that the majority of Calvinists do: claim to believe in cosmological determinism while acting as though my own thoughts and decisions (and thus their consequences for my behavior) weren't subject to determinism.