Both you and the GP are correct, in different ways. Investing in housing development results in houses being built, but investing in land does not. Land values going up are the real problem here, not so much house values. Houses generally depreciate in value, as they deteriorate. In general, no one is opposed to investors who build new dwellings or improve and maintain existing dwellings. The issue is that land ownership is a monopoly which results in land-owners being able to extract economic rents from society without doing anything to improve or maintain or add value to society.

Land-lording and economic, monopoly rents are bad, housing developments and rentals being hired out are good.