A landlord is a landlord, regardless of the particular lease terms. In general, they aren't automatically good or bad. They're just people acting as rationally as anyone else with respect to their material conditions and interests.

If you're asking why they get a bad reputation, I think that's also pretty straight forward:

• Almost everyone has had or knows someone who's had to deal with an especially neglectful or difficult landlord;
• landlords have been engaging in notoriously greedy and abusive behavior since the industrial revolution;
• landlords aren't doing themselves any favors they way some of them publicly brag and whine about being landlords;
• and there's just something that isn't right about owning someone else's home and probably everyone has some faint sense of that.

Personally, I don't think that landlords should be guillotined, but housing policy that's accommodating to them is bad policy. We should be strengthening tenant protections and building new housing to the point that private landlords become practically obsolete.