As far as I know, Jalkh never questioned the Holocaust. He ventured an unqualified technical opinion that Zyklon B could not have been the reason why so many Jews were massacred in Nazi concentration camps. His comments on that topic encompassed about 3 minutes out of a three hour interview. They were wrong on technical grounds, and politically stupid in my opinion. 

As unwise as his remarks were, it's true that Zyklon B was but one of the methods the Nazis used in their pogrom against Jews and others. I only mention this because details matter in law and politics.

Jalkh was turfed almost immediately by the FN. Fair enough.

Marine Le Pen is not wrong in saying the Government of France isn't responsible for the mistreatment of French Jews during WWII. That responsibility lies with the interim Vichy government, and the individuals who lead it under Nazi direction. The Government of France today does owe a moral duty to it's Jewish citizens, and it seems to take that duty seriously.