It seems to me that Denny disagrees because he is labeling luxury items as always being a bad "what it is used for". I also showed how paying 100k on one house would have been better than putting 10k down on ten houses.
To put it in the form as his example:
Two Johnny's must live in a home and that home loan requires 10k down and home value is 300k. Home prices are at all time high and they have 100k.
First Johnny sees that there is a big risk for a housing downturn and puts 100k down on his house. A year later, the housing market collapses and his house is now worth 200k. His payments are lower than if he would have only paid 10K down and has positive equity in his property dispite losing money on his investment.
Second Johnny puts 10k into his primary residence and buys 9 other properties, puttting 10k down. After one year, he still loses the same 100k equity in his house, his payments are higher, and owes more since he is paying interest on 90k more per year compounded. The first year his rentals provided a positive cash flow and he could make payments. However, he still loses 90k in equity X 9 per house equalling 810k debt. His tenants see the decrease in housing value, foreclosures, etc and the rental market also goes south. Johnny can only charge 2/3 of what he originally got in rent and now must find other money to pay his mortgages.