You state the bare facts of which you are certain and let the higher-ups make the decisions. Don't get into details or make moral judgments. These two may both still be your supervisors at the end of it all. Best not to anger either one.
First .. no professional managers would involve employees in their disputes. They should work that out themselves. You should not be put in the middle.
If you are .. and they ask you questions, just tell the truth. And maybe tell them how uncomfortable you are being involved at all.
Tell as little as possible don't side with anyone don't get caught up in office politics or you will lose
i blame obama
You will have to explain your reasons for the conflict. If they are considered unjustified you risk disciplinary action being taken against you.
in HR terms i'd call conflict, productive conflict.
Say a prayer. Do my best to remain calm. Tell the truth.