Ayn Rand was pretty insistent that we should be able to objectively ascertain the facts. Objectivism failed precisely because we're not really all that rational, and because apart from the irrational part of us there's also the fact that we can manipulate perception and gaslight others. If you're a newcomer to a pair of groups that vehemently disagree as to the facts you might soon find that you have to make a choice yourself as to which group to join, and suddenly you have to deal with social pressures not just facts. Do you want to be in the in-group or in the out-group? Can you deal with the shaming that goes with being in the out-group? Etc.

It's all so tedious, but this is what we humans are like.