Honestly, in my opinion the best thing to do is to take them both, or one at a time in the back room and be honest with them, even if it starts hostile over the conversation you are sure to find middle ground. A shift at my store did the same thing to me recently and now I've never been happier while working. This works especially well if they are a friend of yours, sometimes it's best to just let the person know how you feel and how what they say/do affects you.