You are missing the point. Blocking a CDN providers IP range, means blocking all the websites using the CDN - not just the nazi-poster.com.
You run a bar. You let anyone in, and some of your customers are a bit edgy.
But one day, Nazis start using your bar for their regular gathering and you don't kick them out.
Congratulations: now you have a Nazi bar.
Moreover, Cloudflare is the CDN being blocked by foreign ISPs because their laws require ISPs to do blocking on the basis of IP address even though Cloudflare's IP addresses are shared by huge numbers of other customers. It's effectively an attempt to punish international companies for having customers who do something which is illegal in one country even if it's legal in their own country, e.g. some content is in the public domain in one country but not another. It's an attempt to apply one country's laws to another country.
Which is a trade barrier because it prevents a company from serving the customers in both jurisdictions, creating a preference for domestic companies that don't operate in the jurisdictions with less restrictive laws.