Speaking as a fellow forum owner, it's a drip, drip. Forums seldom make money and aside from the financial cost involved do take a lot of effort to create, grow and maintain. When things are good these jobs are no problem because running the forum is a joy, but when there's a constant piss take by certain individuals who take the above work for granted it's very easy to think why bother.
I'm not going to suggest we all play sweetness and light all the time because we're all human so will inevitably blow up now and then. But when you've been warned several times already to cool your temper and still continue then you have no one else to blame.