I think to achieve that you’ll have to redefine the upvote/downvote system. Currently upvoting and downvoting is synonymous with “I agree” or “I disagree”, but what it should represent, is whether a contribution adds or subtracts value from the conversation.
This way if somebody wants to troll their contribution will be vanquished.
Further more, hate speech is usually backed by topics that are indeed worthy of discussion, but are often ill-expressed and prevent any for of civil discussion.