It appears his ASN has quite a few naughty spammers withen. And it looks like these poor people have had their routers busted open by a hacker to turn it into a zombie bot through port 2000.
Click on abuse history.
I interacted with Lumpy through PMs and I checked his IP out with several websites and his router hasn't been turned into a zombie botnet. So the premise that Spamhaus uses subnets, CIDRs or ASNs may ring true based on Stop Forum Spam's data on this ASN belonging to his ISP.
It would be prudent for this website to instead use the Stop Forum Spam API instead of relying on Spamhaus. Waaaay more effective and I use it myself. After all, it's free.