And rereading this thread, particularly your response here (https://news.ycombinator.com/item?id=23447763), that seems to me close to your argument. If not from scratch and first principles, in large part.
If not, care to restate?
It's less the obligation to validate, and more the licence to bullshit, that concerns me. Brandolini's asymmetry is steep. I've spent more time than I'd have liked around intentionally devceptive persons, and institutions (and machines). The experience is virtually always tremendously umsettling, at best.
There are reasons why social, moral, and legal strictures against deception, fraud, and betrayal of trusts run so deep, with frictions against values of free expression. Dante put bearers of false witness in the penultimate circle of his Hell.
When I said "apply critical thinking to all sources", that doesn't mean "re-derive everything from scratch and give zero weight to information obtained from others". "be prepared to question any belief" is closer to what I had in mind. Beyond that, there's little harm in trusting a single source for information you are not actually heavily relying on yourself, but that wasn't really the point of this thread. Are you really trying to argue that the world would fall apart if people generally speaking put a little more critical thought into verifying information they're exposed to from a single source before giving it undue weight?