The problem with this statement is that many people getting into Bitcoin don't understand the underlying concept behind it, nor do they really care. I've spoken to several people who are treating BTC as a new stock investment, and only care about the steadily increasing value and think they can make a quick buck. If Bitcoin crashes (and I think it'll crash to some degree fairly soon) it won't be the core BTC enthusiasts who will leave, it'll be these opportunists getting frightened and leaving in droves.
Now, this may actually be healthy for the long-term state of BTC, but I still think it'll have to happen.
A lot of the people proclaiming "Bubble! Stay away!" are in the same category. Or I'd go as far as to say they don't really understand market dynamics, and the fact that the value of anything is only the price someone else is willing to pay for it. And then there's the people who spread anti-Bitcoin FUD because they are either a) mad they missed out or b) threatened by what Bitcoin offers (maybe they're a rent-seeking middleman who would be rendered obsolete).
I see Bitcoin (and ETH, and others to a lesser degree) as a safe haven. I personally have been selling off stock and moving into BTC, ETH, and others because I think the traditional stock and bond market is grossly overvalued and lacks the utility, censorship resistance, and security of Bitcoin. Nearly 10 years of the Federal Reserve buying up whatever crap people are selling, and building a $4 trillion balance sheet, means the current market prices don't reflect what the market can support.