the first and the most important question that you should ask and try to get to the bottom of it with these people is whether they Truly think bitcoin is in a bubble or are they just talking out of their asses.
if you do, you will be surprised how many of them are talking out of their asses! most of them are parrots repeating some bullshit they once heard somewhere. the others are just spreading FUD in a desperate attempt to see some lower price so that they can buy and make bigger profit or possibly make what they lost because of their idiocy.

otherwise bubbles do happen, bitcoin had at l east 6 major ones in its history, they come and go seamlessly but the drama lingers.