"Rent seeking (or rent-seeking) is an economic concept that occurs when an entity seeks to gain added wealth without any reciprocal contribution of productivity."
What contribution to productivity do corporations or people who have enough spare cash to buy available land provide to a society?
AirBnB can be just a marketplace, that doesn't mean it isn't damaging to society at large. Excluding the moral aspects of that is an ideology based on capitalism, it doesn't mean it's right.
The NIMBY'ism of preventing new housing is the very definition of rent seeking. By legally locking in, the existing owners prevent others from entering the market due to artificially constrained supply. Airbnb doesn't create the demand; they are just a marketplace and one of many.