There are almost many people who knew about Bitcoin long ago but they could not imagine that the price of Bitcoin would increase so much and become a popular currency. So they are disappointed and they often talk negatively about Bitcoin. So it is better to always keep your distance from those people.
Well, to an extent you are right in this point of yours, and why I said to an extent is this; if one who is already in the system and have made profits from Bitcoin on several occasions and someone could/can still give him reasons why he/she should stop his/her Bitcoin/crypto related activities and the person stops, that is where you are right, otherwise, the reasons of such a person who regrets his actions of not investing earlier and now sees negativities in Bitcoin related activities is a person who is scared of taking risk in anything he does, and anyone who has benefited from Bitcoin and give heed to his negative talks about Bitcoin is the one with bigger problems.