Johnny Carson took a public relations hit for the way he came off in that interview and Mort Sahl was never invited back to the Tonight Show. Which, given Carson's clout, also goes a long way to explain the backlash Sahl received.
Steve Allen, the original host of the Tonight Show, had another talk show at this time and invited both Jim Garrison and Mort Sahl on. Unfortunately, and most likely conveniently, Steve Allen also invited wingnut 'B-1' Bob Dornan on that panel. Dornan effectively derailed that interview and Mort Sahl's career had been pretty well derailed too.
Here's an excellent piece on Sahl from 9 years ago in January...
"Heeeere's Justice!" 37 years ago this month, Johnny Carson spent 50 minutes with New Orleans District Attorney Jim Garrison
Sahl is one of my favourite undersung heroes of the Sixties, for having spent the capital of a successful career in the Quixotic pursuit of justice for the murderers of America.
From the cover of Time
to "conspiracy monger"
That strikes me as the trajectory of an honourable man.
There's an interview with Sahl a couple of months later in 1968, before the epochal one-two of Dr King and Robert Kennedy, that is as prophetic as anything I've read from that time:
ARGO: Why is the truth behind the assassination of President Kennedy the last chance of America for its survival?
SAHL: Because the evidence developed by District Attorney Garrison indicates that certain people had to take President Kennedy's life in order to control ours...
http://rigorousintuition.blogspot.com/2005/01/heeeeres-justice.html