Really don't understand what "unacceptable" even means in this context. It is perfectly acceptable for a company to control internet access.

More to the point though, what is this cheap and easy domain scoring system that does a better job than a blanket ban?

The best domain reputation provider, DomainTools, definitely isn't providing their data for cheap, nor is it always the fastest. We pay a substantial amount to them for thousands of requests a day, something we reserve for enriching actual security incidents, not because someone wants to go to catparty.foobar or whatever.