You must be referring to the claim that Churchill let Coventry be bombed to avoid exposing an intelligence asset. That's actually a myth that didn't arise until 1974 and has been discredited.
Section 31 is an unsanctioned, extralegal cabal within Starfleet. It's essentially a criminal organization, a conspiracy in the ranks.
Thank you for this information. I will take the time to read the cited sources. In the meantime, I’m putting “on hold” the argument about the “possibility” that civilians or even soldiers of the same side were sacrificed for a greater tactical good because I concede there's a fault in my argument: Section 31 is not a government sanctioned like the Tal Shiar, the Obsidian Order, the CIA, the KGB, etc.
Now, do I think it’s heading to its fall? No.
1. Section 31 is an extralegal immoral agency with its own agenda but when Starfleet itself needed its help it didn’t hesitate to use it (DS9 “Inter Arma Enim Silent Leges” and J.J. Abrams “Into the darkness”). And based on canon, they have some impressive connections…
2. Mr. Akimoto says: “Section 31 otoh is a complete rogue agency who at times appears to do stuff that's not entirely consistent with the Federation's national interest”. There’s no question they are doing things that are not consistent with Federation values
but doing things that will cause its extermination in the long run would be... illogical
since it has a parasitical relationship with it. The Federation may survive without S31 but S31 has no reason to exist without the Federation.
So, Section 31 has a future? I sure hope so! For the sake of a good interesting plot with lots of posibilities...