Banning someone from your private establishment is within your rights. If they want to run their own business they can elsewhere.
Banning someone via an ISP is different because ISPs have so much infrastructure they can in some sense be considered a "public utility". Nothing would stop someone from advertising ritualistic kitten killing in a public park (except maybe indecency laws but those vary). Likening an ISP to a public park is more accurate. If someone posted a sign saying "no one convicted of smoking weed can walk through this area" you'd rightfully be accused of some civil rights violation in your park. Similarly, ISPs are a conduit no different than a park path.
Everyone chooses KF or whatever as an example of "bad people that should be stopped". That's great. No one disagrees. Anyone with more than a room temperature IQ sees where it goes though. Suddenly you won't be able to access things that don't conform to the government issued public opinion. Don't believe me? The Great Firewall is exactly the same technology.
It is legitimately not my problem, nor the ISPs, who is doing what on the big internet. We have existing laws. Use those to prosecute people posting kitten killing videos or whatever. We do not need to have ISPs using AI and shit as precognitiion to censor what they deem to be "unsafe speech" or whatever.