Well, if they are living in their house, I am not sure why it would matter if the value of it goes down.
They will still have a house to live in.
If instead it is an "investment", well that's the risk of investing. Nobody is forcing them to sell.
It is actually literally the opposite. It is that other people want to have a right to build stuff on property that they own, and the other home owner wants to force people not to do thie, in order to protect their investment.
How about people are instead allowed to build things on property that they own and nobody forces them to do otherwise?
But who cares about them as long as current renters get to take their homes? /s