An NIH-reported study by a Stanford University physiologist shows rather conclusively that facemasks (of the ordinary non-surgical theater variety) are useless against COVID-19 and SARS viruses generally. (It turns out that the reason is simple: The viruses are far smaller than the apertures in the material of the facemasks.)
The author is Baruch Vainshelboim, Ph.D. (University of Porto, pulmonary rehabilitation and clinical exericse physiology), an Israeli formerly on the staff of the Rabin Medical Center in Petach Tikvah, Israel, and now in a cardiological project at Stanford University.
Here’s the Politifact denunciation (which claims a partnership with Facebook leading to the suppression of the post on Facebook). Yet the information that there is at least a genuine scientific debate about the efficacy of facemasks is suppressed. The suppression of the information does not advance the cause of scientific inquiry or the spread of knowledge. One wonders, therefore, what the purpose of the suppression is.
One line of thinking might suggest that the motives are sinister, intended, say, to inculcate in citizens a habit of blind obedience to authority and to condition people not to ask to many questions or to challenge pronouncements presented authoritatively.
Another line of thinking is more benign: It is that some people (including people in authority, whether in government or in the censorship departments at Twitter and other social media) wish to enforce their beliefs at the expense of open inquiry, dissent, evidence of facts that contradict beliefs — a rather common human foible, but one whose aggressive resurgence reflects a certain lamentable retrogression in civilization.