As someone who runs his own consulting business, if I had clients who didn't know what they were doing and abusive towards me, I'd drop them in a heartbeat. The original poster on reddit isn't going to garner any sympathy from me.
I've kicked them to the curb as soon as possible, but not before sending them their source code (at least up until the last commit paid for), server passwords, backups, assets, and whatever else I can find.
I've never, ever, deleted anything or brought a server down just because I was angry at them. And thank goodness too, because half of the time they come back after they've had a chance to cool off.
Telling everywhere, that domain abc.org sucks would result in domain abc.org beeing ranked top, heh. At least it was a creative way of fraud and motivated google for a move, otherwise google would have lost reputation due to that guy too.
However it's clear that this is very bad practice and shouldn't be tolerated by the public.
http://www.nytimes.com/2011/05/13/business/13borker.html
Do not try this at home!
I tried to downgrade my bitbucket subscription to the free plan back before they sold the company, but when I did I just got some error back saying that paypal couldn't charge me 0 dollars.
So I filled a bug, tried again a month or so later and when I still couldn't unsubscribe (I wasn't the only one who had that problem, two others also commented on the bug) sent him a very nasty email, threatening to report him to paypal as a fraudster (impossible to end subscriptions would be a classic fraud technique).
If he had brushed me of rather than told me that I needed to turn of the subscription from paypal I might have ended it right there.
Instead I dragged two other people into it.