This made me smile..

[King Billy]

No they haven't.
The largest party in Nationalism until the end of the IRA terrorist campaign was the SDLP, they denounced the IRA and said they IRA had no mandate for violence.

Sinn Fein didn't contest elections for long periods. (1927- 1957. and during the 1970's)
At other times they were prevented from participating in TV and radio campaigns.
1971–1994 Broadcasting Ban
That Broadcasting Ban was only lifted 4 years before the signing of the GFA.
The SDLP were not subjected to any Broadcasting Ban.