Well really I was just trying to explain the GP's post, not adopt their views, but I think I can play devil's advocate here for the sake of discussion.
The problem with institutional investors is that in making it big business you drive up home prices which in turn drives up the rental prices. Since they can have a wide portfolio of homes, they are less likely to lower rent prices when demand drops, because they can afford to take the short term hit if it they think the market is going to pick back up again. AND they can play games like grabbing all available homes in an area in order to artificially inflate prices.
I see that you did your best, but it should be obvious that the people who want to buy homes also have a massive financial machine on their side, and that it also drives up prices. If the insured 30-year mortgage did not exist, homes would be a lot cheaper.