How the hell would you use LSD in that way "for oppression" or "as a weapon"? The main effect seems to be to cause uncontrollable giddiness and happiness.
The British Military actually tried to use LSD as a weapon. This was the result when they tested it against soldiers: https://www.youtube.com/watch?v=SX7m4fqTLKU
Needless to say, the "weapon" potential was quickly dismissed.
Edit: Here's a US equivalent: https://www.youtube.com/watch?v=NUQNqIIGN88
In short, LSD causes people to disregard authority, act chaotically and unpredictably, lose their ability to follow orders.
It's also highly volatile so likely to backfire on the people administering it, causing them to get high too.
From more direct experience, I can also say that LSD causes you to re-examine fundamental beliefs in quite an intense way. Not at all what you want to use on a population you want to control. In fact, if you were a dictator trying to retain control of an oppressed population, you should probably do everything in your power to avoid mass use of LSD in that population.