The hypothesis is either right or wrong. The data determines that. History shows over and over that progress comes when people push back against the right established "facts".
The parent's hypothesis isn't automatically wrong just because it is an anecdote. Neither is it automatically correct. But people need to be free to say, "Hey, I did this and what happened wasn't what I expected."
Sure, people are certainly free to say "this happened to me", when the subject is aligned. However, the plural of anecdote is not data. Anecdotes may guide research into areas which may be fruitful - but they are never a substitute for proper research.
The parent's hypothesis isn't automatically wrong just because it is an anecdote. Neither is it automatically correct. But people need to be free to say, "Hey, I did this and what happened wasn't what I expected."