Bitcoin fans keep saying "prove it is a bubble" because they do not believe it is - but this is a false question.
The real question all you bitcoin fans should be able to answer is: Prove that bitcoin is not a bubble.
A bubble is when the price of something is far higher than the fundamental value.
Bitcoin gives you ownership of nothing (a stock gives you ownership of tangible assets)
Bitcoin pays no dividend
Bitcoin gives you no right to future payments (bonds give you the right to payments)
Bitcoin gives you no patents or trademarks
Bitcoin gives you no legal rights
Given these facts, you Bitcoin fans need to prove that the fundamental value is different from zero (or close to zero) - otherwise it is a by definition a bubble
This is the probability that bitcoin is not bubbles because until now bitcoin is always very strong. No matter how bad the situation about price dumping but still many investor's believe the recovery of bitcoin. And we are one of them because we are also believed that bitcoin gives us a better future.