Google's review markup guidelines now prohibit including profanity and/or vulgar language in your reviews. So if you have people using bad language in the reviews section of your site and you are marking it up using Google's reviews markup then you must remove the profanity and/or vulgar language to qualify to show your rich snippets and rich cards.
Google added this line to the guidelines:
Profanity and vulgar language are prohibited. Do not include reviews that contain vulgar or profane language.
So you need to step up your review spam detection to remove really upset customers reviews that go above and beyond and leave language that might not be suitable for Google's markup bots.
This was spotted by Aaron Bradley and posted on Google+ where he said "no more f@!ing vulgar reviews, okay?" Indeed.
Forum discussion at Google+.
