Another iteration of this and we'll have bullets with text on them and killing someone with those bullets will be an expression of free speech. The degree to which the 'free speech' analogy is contorted is amazing, more so because the original scope was quite narrow, both legal and geographical.

The problem is closer to a ne'er-do-well taking someone else's signs and hanging them off a bridge over a highway. The person producing the speech is having their speech hijacked for malicious purposes by an MITM; that doesn't mean that it's not censorship when the sign's/webpage's creator gets caught in the censorship crossfire during the attempt to take down the malicious actor.

To put it another way: if someone steals my car and uses it to rob a bank, even if that car is now evidence in a criminal investigation, it's still my car. The police have every right to confiscate it from the thief—it's not their car—but that doesn't mean that it suddenly belongs to them; it belongs to me. In both this case and the above case, I have a right to not be unduly punished for the actions of an unrelated third party (by having my website taken down; or by having my car permanently confiscated, respectively.)

The context here is very similar to a story that was on HN just yesterday (https://news.ycombinator.com/item?id=21671579). Banning a site from the internet for happening to be MITMed by China is very similar in its ethical implications to banning a site from the Internet for happening to have a domain-name that fits a pattern used by a botnet.