As temporary faculty, how to deal with a colleague who, via email, questions agreements made in a meeting?
Actually, I would ignore it. It is fairly typical behavior among some faculty. It might not even be abuse, but just the other person having time to reflect after the meeting. If the comments made were on-topic and not a personal attack, then you have nothing to gain in your current position by doing anything beyond arguing for your position. It could even be that the other person is uncomfortable in meeting generally. 

I once found that offering suggestions for improvement of policy, as a new faculty member, is sometimes definitely not appreciated. I suffered setbacks because I suggested that "the way we do things here" was counterproductive. People don't like to hear that from a new person or an underling. 

But yielding graciously, even if you don't feel it, could put you in a better position for future employment there. 

On the other hand, you are justified in responding to a personal attack, but do so through "channels".