@misohead, since you made two comments I'll reply them both together, is that okay? It got long, so I'll put the comments all under the cut.
misohead
Thanks for the explanation of the difference between lashon hara and motzi shem ra. So motzi shem ra is if you're like "I know this thing is not true of the person, but I'm going to make it up and tell people anyway" ... it's not really something you'd do by accident like many forms of lashon hara? I don't think I have done that, actually. I have spread things that were probably untrue, but I thought they were true at the time... and I wasn't the one making them up.
Honestly, I can't see how one would engage in motzi shem ra by accident, you know? It's very clear cut: someone makes up stuff about someone else, and this gets around, damaging the person's (the one being lied about) reputation.
While someone unwittingly spreading the product of motzi shem ra is not guilty of it per se (key word here is unwittingly), it's still not something that the person will be "let off the hook" for, you know? There's still some serious lashon hara at the very least, but there are other issues involved as well. You need to get your facts checked first before spreading stuff, it really can get out of hand.
Also, depending on your outlook, lashon hara (but never motzi shem ra, because this is strictly malicious) concerns can be overridden depending on the situation. You know for a fact about something that puts or will put someone else at risk? You have to help out. If not speaking about it would endanger someone, this is certainly something that you have to do something about. But really, it can't be just out of "thought you should know" kinda deal, which is just motivated by feelings of vindictiveness, and other negative motivations. The reasons have to be strong.
misohead
and it's good to know they probably don't apply to non-Jews, not because I'm like "oh yeah now I can talk bad about whoever I want," but because I don't have to worry about all the things I may have done without even thinking, or being aware of these rules. I can go forward and do better, especially when/if I convert.
Shmirat halashon in and by itself doesn't apply to non-Jews. But, depending on the interpretation, it could (not saying that it is, but is a possibility if this is interpreted in such a way) be implicitly included in the seven Noachide laws, under the prohibition of murdering, and perhaps stealing also. Purposefully embarrassing someone, for example, is often understood to be under the "do not murder" prohibition for Jews, and I'm sure this could be extended to non-Jews as well as far as the interpretation goes.
If you would like to know more about the topic, I think the easiest book to understand is Purity of Speech. I never got to finish it and had to return it to the yeshiva I borrowed from, but I'd like to get to finish it at some other point.
