@AloizioMacedo:
You are the one making a false dichotomy. Never did I say that we can always classify in a binary deterministic fashion. Some people are obviously quacks, and others are clearly not, and some others or not so clear-cut. And
you falsely imply that I attempt to justify claims that a duck is a duck by relying on it being a duck. It is ridiculous to force everyone to justify every single statement they make, so you cannot rationally expect justification for everything. And if anyone wants my justification, they can easily request. —
user21820 10 mins ago