Bear markets don't lead to assets dropping to zero, otherwise, all stocks would have been long dead now.
I think that his primary point that he's trying to make that most cryptos are worthless, which is true for a lot of ICOs. However, bitcoin is not one of these coins as it actually gets practically adopted, has the trust of the community since it's the first crypto, and is decentralised. No idea why anyone would expect BTC to go to zero realistically.
As they pointed out bear markets are nothing special and generally bitcoin does decline quite a bit before recovering in the next bull market. The professor here is exaggerating this drop by putting it way out of the context of historical bear markets with the same magnitude that has recovered. And it makes sense that they do recover, as adoption is still increasing, and institutional investors are also on the increase.
Nowadays every news portal is trying to get readers with either one of these " BTC will go to 50k soon" or " BTC will be dead by next friday"
Pretty accurate.
There is no real, sensible analysis of bitcoin price in mainstream media overall at this point because of the fact that it does not grab attention of readers. These extreme, illogical predictions are what gets clicks. That's why i think we've got so many of these predictions that if you have any sense of the market, will know that it's not true.