The landlord IS the owner.
They are inseparable. You cannot be pro-landlord and anti-owner, or pro-owner and anti-landlord.
"I'm pro-developers but against programmers!"
"I'm anti-programming, but pro-coding!"
Come on now.
It is in the interests of landlords that as few people owned property as possible. This being pro-landlord is being anti-ownership, numbers-wise.
I'm pro-owernship of property, I'm anti-getting-rich-off-mere-ownership (that is, quite literally, rent seeking).
Someone who only wants the police to have easy access to guns is anti-gun ownership.
Someone who only wants landlords to own property is anti-property-ownership.
And being pro-landlord is exactly that.
TL;DR: all landlords are owners, most owners aren't landlords. And the rent is too damn high.