As a neutral outside reader, this person does not sound like they are hating on your parents specifically, and you come across as extremely defensive (understandably). Their point seems to be that the existence of a good cop doesn’t make the police state tolerable, nor does the existence of a good landlord make the system of people owning other’s homes tolerable.
Regardless of how good any landlord is, it would be better for homes to be affordable and owned by those that live in them. In the current system, some areas are unaffordable without renting, but that doesn’t make the landlords morally good categorically, it means they’re part of the problem that drives prices too high in an area. Owning property to rent artificially drives the price of real estate up. Ideally, renting should be far, far more limited or entirely phased out depending on the specific situation. No one is saying that your parents specifically are evil, but they are part of a larger system that is.
When they said, “I don’t care about your parents,” it was an expression of apathy, not animosity. It was them telling you that they agree, and that their point is about the greater system, not that guy’s aunt or your parents. You took it personally and got more defensive. Their absolute does hold, because it’s in regard to a system. The point isn’t that your parents are individually bad people, like you seem to think it is, it’s that they’re part of a bad system, and regardless of their individual actions, the system is still bad. Fundamentally, you, the other commenters, and I agree. They aren’t trying to argue that you’re defending landlords in general, the argument is that your defense of your parents excuses them from the system.
A fair and kind cop is still responsible for participating in an evil system, just as your parents are. They may be good people, with good intentions, and treat people well. No one is denying that. It’s just entirely besides the point. They’re still hoarding property that should be possessed by those that live in them, and housing should be cheaper. Without landlords and real estate conglomerates driving prices high, there should be a surplus of housing. Again, your parents might be good people, but they are participating in an immoral system. Even the best landlord is still a landlord, and while they are nowhere near anyone’s first target to fix the system, they’re still participating.
The best cop is still a cop, the best billionaire is still a billionaire, and the best landlord is still a landlord. It’s nothing personal against them specifically.