I guess it means you shouldn’t even be mentioning evidence in an “on-going criminal investigation” in a peer reviewed scientific journal in the first place.
The article didn't mention any evidence.
Your argument is that because he DID NOT mention critical evidence it shows that the FBI is covering up some illegal U.S. government bioweapons program.
Have you forgotten your own argument?
Douglas Beecher's article describes established facts from routine microbiology. It says,
... even in a crude state, dried microbial agents have been long considered especially hazardous. Experiments mimicking laboratory accidents have demonstrated that simply breaking vials of lyophilized bacterial cultures creates concentrated and persistent aerosols.
and
While size analysis of freshly prepared powders may bear signatures of the production process and predict some of their performance characteristics, size determinations for material recovered after it has been deployed must be viewed with circumspection. Particle size distributions are dynamic (13), changing as a powder experiences different conditions upon handling, such as compaction, friction, and humidity among other factors.
and
Particles aerosolized from purified powdered spores consist either of individual spores or aggregates of individual spores. The great majority of particles are generally the smallest particles in the population (2), which are single spores in spore powders.
and particularly this statement:
In essence, even if most of a spore powder is bound in relatively few large particles, some fraction is composed of particles that are precisely in the size range that is most hazardous for transmission of disease by inhalation.
So, while he uses such general and well-known established information elsewhere in the article, your gripe seems to be that he was doing something sinister when when he applied such established information to the attack spores of 2001 this way:
Individuals familiar with the compositions of the powders in the letters have indicated that they were comprised simply of spores purified to different extents. However, a widely circulated misconception is that the spores were produced using additives and sophisticated engineering supposedly akin to military weapon production. This idea is usually the basis for implying that the powders were inordinately dangerous compared to spores alone. The persistent credence given to this impression fosters erroneous preconceptions, which may misguide research and preparedness efforts and generally detract from the magnitude of hazards posed by simple spore preparations.
All he's really saying is that it has been long known to just about every microbiologist that simple purified spores are extremely dangerous. He's just adding that any attempt by conspiracy theorists to claim that only spores which have been "weaponized" with sophisticated techniques are dangerous, is just plain moronic bulls**t.
Where's the argument in that?