Yet there is definitely some value in having a clear on the record statement with across the board support stating even what might seem to be the obvious on a communal level.
Part of the problem is that it might not be obvious to everyone that marijuana is a danger to our communities - after all, now it's legal! That is the benefit of putting out a kol koreh in such instances - to make it clear to everyone. Those that choose to ignore it, realize that they are going against the rabbonim, with whatever consequences come with that.
1. I have an issue with Kol Korehs. I think they are overused, abused, ineffective, and counterproductive. Full stop.
2. I have an issue with banning things outright. I don't think it works. Just a personal opinion.
3. I have an issue with THIS Kol Koreh in particular. First, I think the extreme language puts the issue of marijuana in the same league as the worst things we can do. I believe the lack of nuance will backfire. Second, I think that having this on record won't help anything, especially when these same yeshivos and high school will be honoring dispensary chain owners at their dinners in a few years, and putting their names on newly renovated buildings. Third (and connected to the other points), the ban is overarching and leaves no room for any of these Rabbonim or Roshei Yeshivos to deal with issues that arise when the ban is ignored by some. Anything short of kicking someone out of Lakewood for disobeying makes them look like hypocrites and undermines their leadership abilities in the future.
I don't live in this world, so what I say may seem absurd to many here. My personal opinion, which is worth less the virtual ink I write it with, is that there would have been a much more effective way to get the point across, and with possibly better results. Something along the lines of, "We want to address the recent legalization of marijuana in our area. We would like to inform the public that according to Daas Torah, recreational consumption is counter halacha, for the following reasons: XYZ. Further, it most certainly has absolutely no place in our yeshivos and schools, and anyone found to be associated with its use, will be dealt with accordingly."