One of the more effective ways to overcome bigotry is for the bigots to get to personally know people whom they are prejudiced against. The idea is that they learn that the people they were prejudiced against aren't bad like they thought they would be, and personal stakes can develop. But this isn't always feasible or desirable, and some people will never be receptive to change.
My main point here is that the Internet is not really conducive to this sort of approach, not that the above sorts of scenarios constitute an approach so much as a reality that can occur in an integrated society. Online it is too easy to disengage with environments that you don't want to be a part of and reengage with others you prefer. And so: bubbles. And of course there are all the myriad issues regarding actually getting to know someone personally in a way that can translate into real life interactions, issues that I really don't need to go into. In real life situations, like workplace and school, disengagement isn't always an option. Reasoning with recalcitrant trolls and with bots are futile endeavors.
I agree that divisive dialog isn't likely to accomplish anything, but on the other hand, what actually could, online, specifically?