I was concerned about this type of thing happening this election cycle, so what I did was to post a tongue-in-cheek "announcement" on my wall early in the fall. It stated that I wanted to *keep* my friends, so there would be no political discussion on my page. This was really hard for me because I am passionate about my political views, but I have so many family members and friends on the "other side" that I feared some hurt feelings, as some people are unable to sustain a debate without taking things really personally. A couple times, I posted some silly videos with the disclaimer that whatever one's political leanings, they might find them humorous, and those didn't appear to offend anyone.
Removing the heated discussion was exactly the right thing to do. Your wall, your rules. In the past, I removed some snarky comments made by my former sister-in-law regarding, of all things, dog training. My mom's good friend had posted some great advice, and my former sister-in-law said something dismissive and rather nasty. Gone!
Jen Jay, I wish I could say it surprised me that an innocuous topic such as kids' fundraising was turned into a political mudslinging match, but sadly, it does not. Something similar happened to my sister on her wall, (different initial topic, but went all political fairly rapidly.) She chose to allow it to stay up, and I have to admit that it was kind of entertaining to see how far people went with it. It's good that the one relative in your case apologized and moved on. Maybe the other will mend fences now that the election is over?