Khalistani - "Sikhs are not allowed to worship any other guru, sant, whatever."
True, but on Christmas, no Sikhs actually go to church and sing to the lord.
Khalistani - "Nor are we supposed to participate in their religious holidays."
You can celebrate anything you want as long as it does not compromise Sikh principles. Imagine if you were celebrating a Hindu festival (not that I would ever want to), it's ok to jump around and have fun, but you can't go around bowing to some stupid statues.
Kind Regards,
MI