The landlords are keeping the purchase market too high for prospective buyers.
Cite?
If you remove landlords from the equation then the influx of availability can lead to cheaper (relatively) purchase prices, and more people will be able to buy.
Cite?
I presume you're talking about private landlords, but they'll just be replaced by corporate landlords. That's the efficient way to do it anyway since a company can offset mortgage repayments against income, unlike private landlords. Setting up a company isn't exactly difficult or expensive.
There's so much housing out there, it's just not affordable, or available to normal people.
If it's not affordable then even landlords won't buy it: they need to have tenants.