A bit of background: that comedian is being harassed because he's openly anti-semite. France has a strong past with it, for example holocaust denial is illegal (and is so in most European countries). There was also "collaboration" with the Nazis during WWII, something they'd like to atone for.
There is this fine line, and then there's context, history, etc.
What I dread most is the resurgence of the far-right. These events are giving them a huge boost.