Now this is a tricky one!!!
I can, to some extent, understand if people were offended by remarks that are anti their nation. Since you have not posted the 'discussion' itself, it's hard for me to offer an opinion regarding what was said.
However, I do have a problem with the manner in which you were approached about the subject. I find myself wondering - was the owner of the site really involved in this at all? Is this a smoke screen that was used by this particular moderator to express her own feelings, or the feelings of her friends -- deflecting the focus onto the owner and not accepting responsibility for their own opinions.
I say this because, if I was the owner of the site and I felt justifiably offended or even bothered about what you had said, I would almost certainly make my feelings known to you personally. After all, you are Head Admin on his/her site, not just an ordinary member. Unfortunately, I suspect that the owner has never been aware of the remarks you made and that others complained about you and this was the best way that the moderator felt they could raise the issue with you.
In addition, I agree with you that many people make derogatory comments about other nations. As an example, I am quite aware of one particular person from Bulgaria who is referred to as a goat and attacked with goat references on a daily basis. Another person from Germany is constantly called kraut and references made to the Second World War and Nazism. Has the owner of the site, if he/she even reads the logs, no opinion on these examples? If attacking people's nationality is such an issue, is it included in the rules of the site and are punishments dealt out equitably whenever such incidences occur?
If the moderator in question gets an opportunity to read this post, I hope they can offer an answer to these questions.
Spacemariner26