Since 1992 when I saw them use their power to deliberately manipulate the people into believing the economy was bad under President Bush.
I realized back in 1992 they were a Democrat propaganda system, and I've hated them ever since.
It’s hindsight for me, but seeing them say that the economy was on a good track in the late 90s, and then seeing the events from 98/99 and onward led me to realize that they were either lying, or refusing to listen to anything that disagreed with a certain set of politicians’ narratives.