My response would be to walk away until they feel up to playing nicely and apologizing. My mother had to learn that I won't tolerate that sort of bullshit in that exact fashion.
When speaking of various forms of non-monogamy...it ain't poly if you're just fucking around.
While polyamory, open relationships, and swinging are all distinctly different approaches to non-monogamy, they are not mutually exlusive. Folks can, and some do, engage in more than one of them at a time--and it's all good.