I think you're really pre-judging your customers in a bad way here.
You don't have pathological customers, what you have is a large number of people who instead of paying hard currency for a service will trade time as their currency.
What this means is that a good number of those who stay on the free side of the freemium model are in fact willing to pay. Just not with cash. What they're willing to do is to spend time to learn your service, to participate in your forums, and in any way that is required to get their free service.
When you only expect, want, and cater for the customers who have hard currency you will of course piss off the time-as-a-currency crowd if you've already grabbed them.
Then it should come as no surprise when those pissed off people use their time against you.
I'm not saying that's a reasonable response. But it's certainly to be expected. The best thing to do is to work out how to use the time-as-a-currency crowd to your advantage. Instead of ditching them in a price-hike, ask them to do something for you. Maybe they have to participate in support forums to help others getting on board in return for the service? Maybe they have to just promote your service on their site?
My point is simply that it's naive to ignore this very large set of customers, and even more naive to act in ways that will piss them off if you've already constructed a freemium model that attracted them.