On the other hand, perhaps you want to ban or unban an entire domain (all entries presently in the DNS tables). It would still be an issue if an IP address had been reassigned to another domain and amazingly it also happens to be running a bitcoin node, but it seems this situation would be rather rare. Then there's also the issue of IPv4 vs. IPv6 and, specifically, IPv4-mapped IPv6 addresses.

Anyhow, this pull request wasn't really intended to be a complete solution to what is ultimately a far deeper set of issues. It was mostly meant as a quick way to test code (both in bitcoind as well as other implementations) - and in these types of applications one generally would know what IP addresses are under consideration or would be aware of changes to DNS tables.