French is not a race… so I wouldn’t call it racist, really, no matter what he/she may have claimed 
If he called you out for being green, or purple… that would probably be racist (I really don’t know colour of your in game character, mine is green by the way). And I don’t really care of any players real life race 
But if you want, report him in game. There is this option to report in game.
BTW. By showing his/her name here on forums you are violation Code of Conduct: Boundless Code of Conduct No naming and shaming on forums. So please remove the screenshot, and report in game.