I am a PhD student in Europe and also TA for some bachelor's degree classes for my supervisor.
Just by chance, I have found an open Facebook group (normally, the group aims to create an interaction between students and opened by students as well.) in which people in class insult me very harshly about the way I do the tutorial and my personality. (How I look etc.)

How to react or not to react, really? Any suggestions in order to be objective in evaluation of those students?  Because, I don't want to introduce any personal judgemental issue for those who insult when I grade midterms.