Hola, thanks for pointing out this to the AC above. I'm the current maintainer of the AHBL, Brielle.
After a while of maintaining a DNSbl, you start to refine your policies and how you handle things - unfortunately, with the amount of douchebags and assholes who operate mail servers and networks out there, those policies tend to get more restrictive and locked down to prevent abuse.
We used to offer a whitelisting service, where responsible ISPs could register to avoid auto-listing of their blocks. Had to nuke that due to being lied to and threatened (big surprise there). I used to provide free consulting to smaller ISPs who got listed to assist them in cleaning up their networks, securing their servers, etc. Had to nuke that program too - you can thank GoDaddy for that.
These ISPs, the ones that whine about being listed, usually have a good reason why they are listed. They won't publicly admit it obviously, but the almighty buck tends to override the common sense that you need to properly control and manage your own networks. If you are willing to allow your customers to spam, abuse, and just be downright shitheads from your IP space in exchange for money, then you need to be willing to accept the consequences.
The only reason why things are the way they are today, is because people don't know how to behave and be a good online neighbor. In other words...
"This is why we can't have nice things!"