If this guy has never shown any sign of racism to you and has always otherwise been a good guy, whereas you believe her to be untrustworthy and a known shit stirrer... I understand that because it sounded so disgusting that it's really shaken you up, but does the subject matter really alter the fact that you don't think she's a reliable subject to begin with?

If he's a racist you'll know about it. Like others have said, those colours don't stay hidden long.