Genuine question: why not?

There's pretty consistent reporting that rental building owners are earning considerable returns from rent. Rent freezes are one (of several) ways to encourage building owners to reinvest those returns to build/improve properties.

Whether it'll work at large scale is an unproven experiment (Detroit, Paris, Estonia, and many others all show competing possible futures here), but it doesn't seem hypocritical--not any more than, say, the idea of using high tax rates on businesses to encourage reinvestment of profits to drive growth/hiring/expansion.