quincy
Senior Member
You do if you're defending yourself in a slander case because you said he was a slumlord.

Slumlord is one of those tricky words that can be judged either opinion or defamation, depending on context and on how others who hear/read the comment react to it. In a heated argument between John and his neighbor, it can be viewed differently than if printed in an online review.
Either way, though, it is a word best avoided when referring to a landlord. Business reputations tend to be valuable and harming those reputations costly.