Investors and flippers are really bad people, much worse than those who lied to get their mortgages.
Flippers usually added value. They took a decrepit old fixer upper and made it habitable again. I don’t have any problem with adding value. A friend of mine used to buy houses, keep them for about four months, and renovate them top to bottom with huge amounts of risk capital. Then he would sell them and make a profit which was his income during the four months. It was a risky business and he was rewarded well for putting his risk capital on the line. And the neighborhoods were enormously improved by having a blighted eyesore turned into a nice house.