sure that's theory.
But think about some really sensitive shit comes to hive. For everyone readable.
Maybe something politicians hate and they see it is impossible to censor because of XYZ frontends.
So the witnesses would be IMO the easiest target to hit.
Will it be successful? Most likely not.
You're kind of arguing that nobody at all would want to be a witness, which I find very doubtful. No doubt some current witnesses would drop out even if not directly targeted.
Considering the possibility that we could end up with more anon/random witnesses, we ought to be taking a look at some of the security assumptions currently being made that depend on witnesses getting voted in on reputation and not wanting to misbehave because they could get voted out. That would be weaker if witnesses are anon, but maybe not entirely gone as long as witness rewards are high enough.