Quran 8.39 (or 8.40 if we consider the besmele as a verse): And fight them until there is no persecution and religion is wholly to Allah. But if they desist, then surely Allah is Watchful of what they do.
Muslims were enjoined to fight till religious persecution had ceased and men were free to practise the religion of their choice. Islam undoubtly is the greatest upholder of freedom of conscience, as was read in Quran 2.193 (or 2.194 if we consider the besmele as a verse): And fight them until there is no persecution, and religion is professed only for Allah. But if they desist, then remember that no hostility is allowed except against the wrongdoers. This verse also shows that Muslims are allowed to fight in self-defence only when war is inflicted upon them by the other party and to continue it till complete freedom of religion is established. The Holy Prophet Muhammad (pubh) could not have entered into a number of treaties of peace with disbelievers if the Divine commandment had been to continue fighting until all disbelievers had embraced Islam.
And actually there is no an islamic punishment against blasphemy. There is also no punishment to you if you are not muslim. the important thing is always PEACE in islam.
if muslims were in favour of war, they would certainly put forward the words of Jesus against Christianity, which are:
(Matthew 10)
34 "Do not suppose that I have come to bring peace to the earth. I did not come to bring peace, but a sword.
35 For I have come to turn
" 'a man against his father,
a daughter against her mother,
a daughter-in-law against her motherinlaw
36 a man's enemies will be the members of his own household.'
They have a great respect to Prophet Jesus and they accept him as a righteous person sent by God. They don't accept the sentences above as a war-yell, as Christians don't accept too.
Regards.