I don’t understand how you come to that conclusion. You are right that you can’t change the “view” of a troll because - as you have pointed out - a troll actually does not have a view on a given subject but only a agenda with inflammatory “talking” points.
But when you discuss with people who are ready to change their view or consider the views of others you can very well change their believes. There is nothing inherently worse in online discussions which prohibits this. It might be easier in real life, but still. I know for sure that I have changed the view of people just by online discussions with then. Or how do you call it if someone tells you “Hmm, I think you are right. I was missing the point you just showed”? I would believe that most of us who engage in online discussions have changed the view of someone at one point, be it on a minor or major topic.
Reddit’s “changemyview” subreddit is an interesting example of that. People regularly change their view slightly or profoundly after discussion there - or at least they claim in a convincing way. Even more, some people show up there with some view they feel bad about and actively seek for help and arguments in changing their view. I would argue that for such cases a internet discussion might even be preferred as it is much more easy to find people who can share another viewpoint (e.g. out of own experience) if you have a big pool of people who might unlike when you meet a limited number of people in real life.