I don't think they are unstoppable, especially on steem, this is such a thoroughly saturated population of critical thinkers that trolls hardly get fed. I have also helped bring down trolls here, and they can't do anything once they lose trust or credibility, they just exist stage left. What's interesting about trolls, if you troll them hard enough you should have a very good idea exactly how and and in which direction you want to take things, and you can usually hang them with their own words or logic and string them up.