A Gorilla Tactics ban doesn't set a bad precedent at all, we literally banned Power Construct in Gen 7 to nerf Zygarde. I don't know why you are mentioning complex bans, when people have not been asking for one. If Darumaka-G also had Gorilla Tactics, then banning the ability makes no sense because only one user would be broken.
Moving unto your example about banning moves, moves have only been banned if they induce an unhealthy amount of RNG (i.e. Sheer Cold, Double Team, Swagger in Gen 6, etc). King's Shield and Sacred Fire are great moves, but neither induce RNG, so banning them doesn't fit with how Smogon bans things.
Additionally, when a move or ability is banned, it's banned on everything. So comparing the argument to something as rediculous as "let's try banning Sacred Fire on Ho-Oh" is disingenuous to the side that wants Gorilla Tactics banned. They are not arguing for a complex ban, they're arguing for a simple ability ban.