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.
I started to ban individual IPs, but they started changing their last octet, so I am now banning the last IP range.
0.tor.exit.babylon.network 149.202.98.160
0.tor.exit.babylon.network 62.141.45.12
1.tor.exit.babylon.network 149.202.98.161
2.tor.exit.babylon.network h 149.56.229.16 212.117.180.21 149.56.229.16
3.tor.exit.babylon.network h 149.56.229.17 193.111.136.162 149.202.98.161
4.tor.exit.babylon.network 212.117.180.21
4.tor.exit.babylon.network 178.17.174.99
5.tor.exit.babylon.network 212.117.180.130
7.tor.exit.babylon.network 178.17.170.201
10.tor.exit.babylon.network 193.111.136.162