Locking Out the Undesirables

After the class discussion on whether or not people who committed crimes -- genocide, for example -- could be included in a discussion to reach a consensus on morality, and the general conclusion that they can't, it seems obvious that this implies a social contract in which members can only participate as long as they follows the rules. However, it appears that it would become increasingly difficult to determine whose opinions are acceptable. Is there really an objective standard of right and wrong (such as, as Lynch offers, a universal morality/"obligation to protect the innocent") that participants must adhere to?

Although that is a somewhat unpopular perspective, it's also pretty unpopular to actually listen to someone who argues against certain universal morals, i.e. argues for genocide. In that case, what are the terms of this universal morality? Does it only go as far as genocide, or are there other actions that are widely accepted to be crimes? Terrorism comes to mind, and I think that this is popularly considered wrong; it also appears that terrorists automatically lose their right to participate in a consensus on morality. It seems to be an issue of credibility; if you're trying to determine whether or not an action is moral, you don't consult someone you consider immoral.

However, if there were to be a discussion on morality, it would be interesting to see whom states were actually willing to invite; although we consider terrorism and genocide wrong, we do tend to prop up dictatorships and stand by while genocide occurs, which could be considered equally wrong by other states. Would we be considered too immoral to participate?