It's better not to give advice to this kind of problem because in the end when our advice is contrary to what happened we are the one to blame. Just say to your friend that it is up to him to decide whether to hold or sell his crypto.
To be sure, don't easily believe what people say and it's better if you really need advice or a solution, ask a competent person,
but if we really understand I think there is nothing wrong with us giving suggestions it could be that it helps,
apart from that all in my opinion it comes back to their respective decisions