I wholeheartedly agree that landlords should not engage in abusive behavior: Landlords should not discriminate on the basis of protected class. They should keep units safe and up-to-code. They should not engage in deceptive practices like advertising one unit and selling a different one, or falsifying facts about the unit.

But where I'm not going to agree is the notion that setting rent above a certain threshold is "abusive landlord behavior". If a landlord is setting the rent too high, the consequence should be that the unit stays vacant. If someone is willing to pay that rent, then evidently the rent wasn't too high.

Except that there are significant switching costs. A person moving has to pay moving costs, might have to replace furniture that doesn't work for the new place, can affect your children's schools etc. This means the value of a unit to someone living there can often be significantly higher than the market rate.

This can led to situations where the most profitable move for landlords is to take advantage of the discrepancy to regularly raise the rent for existing renters by more than the market, in attempt to maximize profit. Sure they might have to deal with the hassle of finding a new tenant every couple of years when someone gets priced out, but if it leads overall to slightly higher profits it's the winning capitalist move.

The rentiers are ostensibly following the law, but the overall cost to the population and quality of life loss to renters can be significantly outsized compared to a sliver of additional profit for the rentiers. This is a great example of externalized costs in a free market and exactly where government should generally be attempting sensible regulation.