Vitalik's comments are completely reasonable, and provably what any traditional finance advisor would say. Completely in the mainstream of financial advice. Very naive of you to say he is young and doesn't understand markets. He is young, but smart enough to know that what he is reporting is excellent traditional financial advice.

The only point I agree with is - "why is he saying these things? what is his motivation?"

Since he is not a financial advisor, why does he feel compelled to repeat that type of advice?

He may have legal advice that he will be better positioned to defend against future claims of fraud, if he regularly sends out this type of information, prior to a large crash of ETH