You need to understand that context is important. It’s clear that they are not against people like you, and that as I stated, they are using the term Landlord more as a job title than as a status of owning a rented house. I have already agreed with your arguments, I’m just saying that if you present yourself as the term that people have coined for “house-hoarders”, then you are going to have a bad time, even if technically that term is being misrepresented in the given context.
You shouldn’t tell them that they are wrong on blaming landlords, because what landlord is for you and them is different, you should tell them to find a better term, at most. The better way to approach this would be to ask for clarification of what they mean with landlords, and while for sure there will be extremists, people in general will agree that what they hate is house-hoarders and landlords that speculate with property, not people that own 2 houses and rent 1 of them to help a bit with finances in a fair way.