It's different in that I can accept a cash payment from you without having to worry that your cash will somehow harm me. Not so with a request coming from an IP address from which malicious requests are known to originate.

So with cash, people can disagree on its benefits and drawbacks to society as a whole, but as long as it's legal, there's little reason for me, individually, to not use it, regardless of my opinion on its value to society. With IP addresses, I might conclude that I'm much better off blocking some even if I lament the consequences of this for causes that I approve of.