Cross-quoted this because I didn't want to start a discussion in the Chapecoense thread.
Regardless of how tragic this crash is, and how nice the gesture is, Cavani knows what the rules are, and he broke them. Basically Cavani deemed the consequence of receiving a yellow card worth the action of showing support for Chapecoense. Which makes the gesture even greater in my opinion.
As for the referee, Cavani is standing there with his shirt gone, and there is no way the 4 referees don't see it, and there's no way they can all pretend not to see it. He has to give the yellow card, and suggesting that the referee should not officiate another match this season for following the rules is ridiculous.
The French FA can have a look at it, and consider rescinding it, but I honestly don't think they should. That would leave the whole rule about removing shirts and what statements are allowed open for interpretation.
@top1whoisman @Peyroteo