Plus usually when people are trying to push that argument, don't they claim it was about blacks not Mexicans? >_>
You're thinking of the difference in penalties between cocaine and crack, which indeed was to hurt black people. And on the matter of cannabis, it was quite explicitly made illegal to fuck over Mexican Americans. This is so well-known that searching just now for "why is cannabis illegal in the us", the first result's blurb (from History.com) was: "Fear of Mexican immigrants led to the criminalization of marijuana."
So no, just because you don't know the history of something doesn't mean it's paranoia. It was a conspiracy, but a real one. They do happen, and our country has a long and storied tradition of fucking over minority communities.