Actually, that's... not a terrible idea. It's not the best idea, but pulled off right, a simple "we'll help you but if it's not a security issue, site downage or a serious harassment incident you gotta pay" is way better than current help models for social media/large sites.

It's not the user's fault if the business model isn't sustainable.

Sorry, but no. This isn't acceptable. The value in their product is the people. Cutting them off, without discussion means they are selecting their product choice. If a human did this, based on a complaint (perhaps), they can talk to both sides - not just the complainant.