tor.exit.babylon.network: Research, Ban
The whole concept of tor is a sound one, allowing those in repressive or privacy-optional countries (Canada, US) to anonymously use the internet. Unfortunately this anonymity has been hijacked by the spamming community, taking a benevolent tool and using it for ill. Any IP or hostname used for spamming is game for being banned, tor or not.
tor.exit.babylon.network has a network of tor servers that are content spamming me. Normally tor server IPs are stable, so once you ban them they stay banned. These guys move around a bit, and there are a number of them. If you ban a tor server, or any other hostname, and they return to spam again, then you know they evaded your security efforts. You need to do more research.