> It is justifiable to critique them in whether or not they've done a good job of that,
If the announcement said "all disinformation about Russian-Ukraine conflict" it would grant benefit of a doubt about their execution as you point out. But it says "Russian disinformation" thus they are making it about politics (something a search engine should not be doing), not fighting disinformation (something a search engine should be doing), so we are justified to critique them on that basis.
> You know that most search engines downrank non-English-language sources for you if you're located in America, right? They try to return results in languages that you're likely to be able to read.
Correct. Because they can rightfully infer that the user is searching in english and likely wants results in english. However in this case, they are inferring a certain political view of the conflict, regardless of what your intent is (what if you are a Russian or Chinese DDG user, or simply someone who is agnostic and wants to read what all sides have to say to form a world view?). No basis for inference can be established here. The only way this could work is by having a switch in the interface to turn such results off, so the user can opt in into it if they prefer to.