Doesn't that mean that accepting/rejecting any statement relating any information, whether about facts of material existence or, say, how society should be governed, would simply be a matter of personal choice?

In the end any human being has the capacity to choose to accept or reject any information received from any other human being, but to negotiate material existence successfully we have no choice but to recognize that beliefs as a form of knowledge and 'natural facts' as a form of knowledge are two very different things. That's all I'm saying.