The organizer, Masoud Alam, is quoted as saying, "This is not freedom of expression, there is a limit for that. This insult of the Prophet will not be allowed... Until it is banned we will keep protesting."
Yes, it will be allowed. In a free society, just because you label some belief as "religious" doesn't mean I can't criticize it. And you are free to lie and say things like, "Prophet Muhammad is the founder of freedom of speech", and I can criticize that, too.
Islam is badly in need of a reform movement.