On what grounds would you sue him?
I mean you as a lawyer are probably more qualified than I am, but I don't think anything he said should be a sueable offense. He even said that he thinks Deschamps isn't a racist.
Slander. He may not have said Deschamps is a racist, but he has painted him as a coach who is clearly unqualified for the job, because his decision making is influenced by racist groups. That clearly hurts his reputation and thus may cause him to lose out on other opportunities in the future.
I also think the French FA should respond and try to look into whether they can ban Benzema from all international games for at least a year or two. His comments are completely unacceptable and are inflammatory. They also aim to victimize a certain group of the French population and do so right before the kick off of a tournament that is already facing serious threats of terrorism.
I honestly cannot believe Benzema could be this stupid. I sort of liked the guy before (I thought he was underrated at times), but I almost consider him subhuman now. Fuck him.