It is essential to ask what causes blasphemy. In most cases, religious clergies are themselves responsible for it because they fail to project true Islam. Why blasphemer or those criticizing religion can’t be scrutinized, enlightened with the truth and leave the rest to the Almighty.
After all, if the idea is to promote truth blasphemers should be heard and their understanding corrected in its true light. Enlightening an offender is better than silencing them. But most clergies are too emotionally blind that makes such punishment subjective, to vent their own furor.