These aren’t truths. It’s cases like “is the earth flat?” that have an answer in objective reality and people still argue about it where some people are simply wrong.
It's what people consider and call a truth. Language terms are defined by use.
And people absolutely argue, fight, unite, or even go to war, for the version of those that they'll consider and call the truth of such matters.
“sincerity in action, character, and utterance” is different than “the body of real things, events, and facts”
This distinction very much exists in how people talk about such things. You don’t need to “have faith” that something like gravity exists such that when you trip you can fall down. “We hold these truths to be self evident” isn’t how you talk about the distance between NYC and Boston.