Mao wants to know your location
Jokes aside.
The problem with landlords is exploitation. Their concept of ownership of land is that you own it so you can do whatever you want, in sense of exploiting it's resources or, in case of a house for example, renting it and expecting a revenue for doing nothing. They, the landlords, are parasites that want to get value from something without doing anything and people in the "western world" (using the term for broad clarification) justify that. All of this does not mean that a landlord cannot be a socialist and help the cause in some way, like Engels but he was a member of the capitalists. Still, without destroying the system that permits all of this, even if there are landlords that are indeed communists, the status quo will continue with all the exploitation that follows it.
Clarify me if I'm wrong comrades, please. I'm still always learning.