If the political conversation was polite and reasonable, I would not think it rude. But, in this case, it is loud and disruptive, therefore, rude.
Today, it seems that a hostess's duty is mainly to distribute drinks, check the food and open the door (ok, I am exaggerating) and that her most important duty has fallen out: that of keeping the evening pleasurable, facilitating conversation and making sure everyone has a chance to shine or that no one dominates the evening. In this case, if some people are enjoying the heated exchange but others are feeling awkward, a good hostess should gently redirect the conversation, if possible, or do so more directly, if it is getting out of hand.
Personally, I like a good political debate but I hate shouting matches. I would redirect him every time the subject came up, before it could evolve into an actual conversational topic.