All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
It is a fact that the Jews work sincerely for the sake of their falsehood and distorted religion. They achieved overwhelming superiority; but surely, their end will be extinction. The main reason behind this is the retreat of Muslims from leading the world because of indulging in worldly affairs and neglecting the right of their Lord.
However, this would not change anything because they are misguided whether or not they are sincere. Once Ibn ‘Abbaas was asked, “Why do the Jews not forget in their prayers?” He said, “What does the devil have to do with a ruined heart?! Allaah The Almighty Says (what means): {the [best] outcome is for the righteous} [Quran 7:128]”
So, sincerity brings about praise and admiration for the person only if the deed itself is righteous.
Allaah Knows best.