Relativism and moral noncontroversies

When we ask whether morals are relative, we often look at very difficult issues like abortion and say that there is a good deal to be said on both sides of the issue, and that it is hard to say what is really right or wrong. (Unless you are talking to a dyed in the wool pro-lifer. Then abortion is wrong because it's murder, and everyone who thinks otherwise is just wicked).  What is actually problematic for relativists are not the highly controversial issues that we argue about all day long, but rather the issues that look to us as if they are pretty cut and dried. For example, if relativism is true, then it is only relatively wrong to invite someone over for dinner, shove them in the oven, and cook them as dinner. If a society approved of pedophilia, or slavery, or something like that, then it is a mistake to condemn that society as having accepted a bad moral principle, however one may personally dislike that rule oneself.