A twisted choice of words. If I write that someone said something, and provide the source in which he said it (e.g., a book with his name on the cover as the author), I’m not relaying “hearsay” about his opinion; I’m relaying his opinion. Given your objection, you might as well say that every time you cite a scientific article, you are treating the contents of the article as “hearsay.” So if Wikipedia said, “Many scientists have said that ID…” and provided notes with examples of those scientists and where they said what they said, that would not be invoking “hearsay,” it would simply be documenting the claim that many scientists said something about ID. And I’m all in favor of documenting that people said what they are claimed to have said.
Non-parallel examples. First of all, it’s not “many” scientists in your examples; it’s “all”. Second, your examples are statements of facts about nature (or in the middle case, a fact about how chemists depict nature formulaically), not disputable verdicts (I remind you of the never-solved Demarcation Problem) about, e.g., which activities count as scientific and which don’t, or, e.g., disputable theological/philosophical verdicts about whether ID is creationism. I have no problem with encyclopedias reporting facts about nature, as universally agreed upon by scientists, without a prefatory phrase such as “All scientists say that.” I do have a problem with encyclopedias reporting characterizations of theories or movements or philosophies as if those characterizations were objective facts rather than the judgments of the people offering the characterizations.
If you mean, how many of the commenters equate any endorsement of “evolution” with “atheism”, then not many. There is a wide acknowledgment of the possibility of affirming “evolution” (understood as descent with modification) without being an atheist, materialist, etc. (And many of the ID people in the discussions themselves affirm evolution in that sense.) In fact, most of the discussions of articles and books about evolution are about strengths and weaknesses of proposed evolutionary mechanisms, without any reference to the religious beliefs of the writer who is proposing the mechanisms. But if someone like Dawkins or Coyne or Dennett is presenting evolution as a weapon against religion and evidence for the truth of atheism, then yes, sometimes the charge that a writer is motivated by atheism will come up. But in such cases, the writers invited such a response, so there’s nothing improper about it.