Then don't comment on their site? I mean if you're looking for discussion online, there are thousands of places to go. But this is specifically about the comment sections they provide. It seems entirely reasonable that a room they provide should be subject to their rules, and one violating those rules should be shown the door.
They never said that Talk was aimed at moving that goal further along, however. They're trying to use it instead to allow better curation tools to make comments manageable.
It seems that their goal is to help sites move away from 3rd-party comment management services such as Facebook and Disqus. Based on this discussion, I think federated (not site-owned) comments are the way to go long-term. Maybe Talk can eventually be adapted to help with decentralized comment moderation.