Welllllll... I am NOT pro-rent-control/stabilization/etc, but I will point out that an existing landlord has some monopoly power over his tenant because the cost of a new apartment search and move is high (in terms of finances, effort, time, emotions, new neighborhoods, lost stability, etc). The free market is only efficient if transaction costs are low, among other things.

But then, on the other side of the equation, every place that has rent control also has the risk of foregone future rent increases baked into the price. They'll also have insane leases meant to minimize that risk. If there is an imbalance of power between the tenant and the landlord because of their relative conditions, the government really has very limited power to change that.