how about overwhelming evidence?
The very term "conspiracy theory" is a manifest scheme to control
permissible public discourse. Overwhelming evidence is what generally
convinces me. For example when I saw the 1963 Look magazine
photograph of Oswald standing in front of the TSBD building while the
Kennedy limo drove by, or when I saw the original Zapruder film of the front
of Kennedy's head getting blown clean off. Skepticism is intellectual
dishonesty when evidence is overwhelming.