How can someone criticize Islam or prophet Mohammed in an academic or theological way without being accused of aggression to Islam and its prophet and consequently punished or killed?

Anyone who wants to criticize Islam or any other religion or any opinion should follow the objective method to that. He should be impartial for any desire, he should not have any beforehand opinion before studying that, he should study the matter fairly and considers it from all sides, by merely scientific observation he should seek true scientific inference away from any desire or fanaticism. He should mention the advantages and disadvantages side by side if there are any. His tongue or his pen should abstain from curse, abuse, insult, offense, falsehood and perjury. A critic who follows these bases has worthy and considerable views; no one denies or neglects his views. There are several examples for such critics among orientalists, European philosophers who followed this method and all accepted their results.