The question is do you have the power to blapheme? In a free society we do. Do you have the right is up for grabs and dependent on circumstances. If a religion is really a religion respect for it would proably be in order. If a religion is a cover for immoral and violent behaviors it should be condemned even if its adherants cry blasphemy. Perhaps there is even a duty to do so.
We need to start making fine distinctions and act prudently and courageously. Right power duty prudence courage respect.
I think by Islamic doctrine to say “Jesus Christ is the son of God and only trust in Him results in heaven”, is blasphemy of the highest order. Thus any true Christian would always be insulting Mohammad by being in disagreement with him. One could not say that Allah is not God, nor that Mohammad was not a prophet without being blasphemous. Thus if blasphemy against any religion is illegal, All Christianity, even within the walls of a church, would be illegal. Since each religion in some way contradicts other religions, all religions would be found blasphemous and illegal other than the one followed by those in power.