Ken Keathley has good advice for when you are writing about those with whom you disagree. In sum he offers three good suggestions.
1. Describe your opponent’s position in such a way that he can recognize it.
2. Know your opponent’s position well enough that you could argue it for him.
3. Write as if your opponent and you were going to dinner together after you finish
I often find that advice like this is sadly neglected on discussion lists, blogs, and other forums like Facebook. This is also one reason that I don't often interact with discussions in these contexts. In any case, Ken's post is worth reading in full here.