A good friend from TX (now deceased) was politically well-connected, including being personally acquainted with Lady Bird's press secretary, spending time at the White House, etc. He would talk to me openly on virtually any subject, but when I asked him (in the early 70's) what he thought about LBJ's possible involvement in the assassination, he immediately got a stony look on his face and wouldn't speak until the subject was changed. FWIW...
Perhaps he wouldn't speak because the idea was and is, considering the lack of evidence, ridiculous? I really love how conspiracy theorists whine about the evidence presented in favor of the so-called "official story", but they never provide any evidence for their own stories.