I will try to interpret, but obviously it is just my interpretation (and personally I mostly agree with many theses Burry gave). First, he does not really talk about being a "good citizen" or not. His points are for "greedy citizens" who, in his view, should be worried (about his pocketbook) if he is heavily invested in passive index funds.
This is due to his "bigger and bigger crowds, same exits" analogy: individuals easily move through doors at will; but if a crowd rushes out through the same door, injuries happen.
His premise is that many stocks that index funds invest in have low liquidity (small door): half of stocks in SP500 trades less than $150M a day. This is tiny (he quotes total market cap of indices of $150 trillion). What happens if there is a small, but synchronized outflow for any reason? If customers ask for 1% of index funds to be sold, index funds have to sell 1% of their holdings in the exact ratios defined by the index, including stocks with low trading volumes. Which is a problem, as there may be no one to sell them to, so prices of those stocks may crash and create a big panic causing additional sales of index funds bringing down bigger chunks of the market.
That is the gist of it I think.
This is due to his "bigger and bigger crowds, same exits" analogy: individuals easily move through doors at will; but if a crowd rushes out through the same door, injuries happen.
His premise is that many stocks that index funds invest in have low liquidity (small door): half of stocks in SP500 trades less than $150M a day. This is tiny (he quotes total market cap of indices of $150 trillion). What happens if there is a small, but synchronized outflow for any reason? If customers ask for 1% of index funds to be sold, index funds have to sell 1% of their holdings in the exact ratios defined by the index, including stocks with low trading volumes. Which is a problem, as there may be no one to sell them to, so prices of those stocks may crash and create a big panic causing additional sales of index funds bringing down bigger chunks of the market.
That is the gist of it I think.