Landlord's who pull this sort of shit are retards. Threatening your tenants and pulling stunts like this is the surest way to ensure that your tenants will be living in your property rent-free for a good long while... if not owning your property outright. I let formal letters and e-mails and eviction notices do all my talking and threatening for me. The LEAST effective way to get rid of deadbeat tenants, or get paid by them, is the 'face-to-face and belligerent' method.
Oh, I have so wanted to board up the windows and doors of some of my properties and torch them with deadbeat fuck tenants inside. It would've been worth the loss of the property to hear the screams as those shitbags roasted alive.
My chick has seen some interesting things when she was a health inspector... like land lords turning off water/gas/electricity intermittently or tenants dumping clumping kitty litter down the turlets...