In that case, if the area is claimed a screenshot of the obscenity with visible land ownership and a screenshot of the /whois of that username in the chat would be possible. Or if you are using the mod chronicler the output of that, showing who built those obscenities plus the aforementioned /whois screenshot.
And no, I don't support racism at all and told you we got a zero tolerance policy for that - but at the same time this applies to putting people at the public pillory, especially with zero proof. We generally do not tolerate namecalling.