It's never ok because it only makes whatever system you are trying to pressure to recoil in defense instead of giving up what you want, any kind of accomplishment from dissident groups has been made in most cases by swift and strepitous action, it would be foolish to make threats and wreck shit when you have the short end of the stick.
Besides, I firmly believe that because of the aforementioned, terrorism is almost exclusively resserved to controlled opposition shaping public opinion and behavior in ways you wouldn't normally be able to.
Let's take for example the recent french attacks, let's for the sake of argument pretend the attacks were stages by the french goverment due fear of a civil uprising in the light of the immigrant invasion, propaganda has become useless due the magnitude of the event and political appeasement probably won't cut it either, so, how would you deal with countering the tribalistic sentiments from the waking population? easy, you organize a false flag attack led by the "refugees" those with common sense loathe and those brainwashed love, both will demand goverment intervention and according punishment for different reasons (simple logic and contrived "not all muslims" bullshit respectively), but said course of action will require aditional steps, such as a curfew, massive house searches, border clossing and probably even martial law, alongside other meassures that under normal circumstances the people wouldn't stand, but in this instance they will gladly cooperate, because they believe it's for their own safety and to catch the perpetrators of the massacres, and some even that it's the perfect excuse for a retaliation against the brown hordes , when in reality the criminals "do not exist" and everything was a simple ploy to keep the population in check in case they get fed up with their miscegenation program.