Its much better to allow the opponent to express their facts, views and knowledge. Then where you can, debunk them with your facts. Allow them some breathing room to continue the debate but you can still control the direction buy picking one of their facts you can positively argue. But keep in mind you must spark their interest (and other readers) and keep the amount of information to the minimum and on point. The idea is to paint your opponent into a factual corner where they must either contradict their original views, concede or agree.
Try (I know this is difficult) to ignore your feelings with their arguments that hit a nerve. Seek comfort in your sources in order to fortify your views.
I've learned more, here on this board, with spirited and lengthy debates. Especially when I'm actively involved in the debate, I end up teaching myself new and unknown avenues of history. Its very rewarding. There's nothing wrong with both sides finding common ground.
David