Just let people sell their Bitcoins out of panic. They must regret that they sold Bitcoin too early and only panicked when they saw the price decrease. Now is a good time to continue the DCA strategy because Bitcoin is still not rising too high.
I don't want people to experience the panic that I've made before and that's why giving them some advice on what they should do about holding is like a responsibility if you know that they're making a mistake.
But that should stop there because once you already told them your advice, they're on their own already and it's up to them if they're going to follow what you have said or not.