Yes he is wrong. This is a non-sequitur. He is offering a conclusion that does not follow from his argument. Why should the lack of liquidity cause a bubble? Usually lack of liquidity acts in the opposite direction. It causes prices to go down not up.

Furthermore, the bubble dynamic usually requires liquidity. The bubble dynamic happens when prices are going up so much that participants do not care about an underlying valuation but are certain they will be able to sell in the near future for a higher price due to the market momentum. This whole way of thinking, requires liquidity.

If there is indeed a bubble, I do not see how it can logically be caused by lack of liquidity.