It would be a significant mischaracterization of the state of the evidence on both those issues to say there is all that much room for interpretation.
A more likely reason for holding the extremist position of an anti-vaxxer or climate change denier is the usual cognitive biases against incorporating new information inconsistent with one's current mental model.
A more likely reason for holding the extremist position of an anti-vaxxer or climate change denier is the usual cognitive biases against incorporating new information inconsistent with one's current mental model.