It does not block all of cloudflare, it blocks their shared IPs. If you are doing serious business you may not want to do it on IPs that are also used for shady content. IP reputation is a well known strategy, used by emails and other firewalls.

Okay, so they aren’t blocking whole ranges. Yea, you definitely don’t want to share an IP with a spammer or malware site. I thought they were blocking whole ranges.