[PeterisP]

First, it's literally impossible for all of the "active investors" to take their money out as cash; some active investors can cash out by selling all their stock to other active investors who think that this is a good time to buy more stock; passive investors would/could only absorb that amount of stock at the speed of new passive capital coming in, which is gradual, not that large (compared to the flows of active investors) and would likely slow down somewhat in a market downturn.

Furthermore, how exactly are "passive investors" going to take a bath? They're simply making a very long term bull market bet; if DJI drops 50%, it's the active investors that might sell at this price, but the index funds will just keep their position until (and after) it recovers, the only case where they'll lose in the long run is if the DJI drops permanently and that doesn't seem plausible outside of ww3 scenarios.