Good post, you have nicely summed up in a nutshell why organized religion is detrimental to society, and why this problem of violent outbursts will continue, unless changes occur that fundamentally alter the way how people think. Through a reformation that encompasses and implores educational, political, and psychological transformations. Just saying 'Islam is a religion of peace' is a mockery these days.
Your question has substance. But only if the other side is willing to employ logical reasoning. Looking at the pictures with those enraged and violent rioters, do you honestly think that they will listen to reason? No, they are completely brainwashed, devoid of any rational thinking, who can be charged up, with emotional ranting and demagogue, to attack anyone who 'insults' Islam.
The mere presence of non-Muslims in their midst is blasphemous to them. How can you reason with such people, who will slit your throat without the slightest provocation?
Coming back to your question. What you say is correct. It is impossible to protect the religious sentiments of the Muslim on one side and the Christian one on the other side, while still insisting that people may not criticize either beliefs.
For example, the very distinctive position that Muhammad takes in Islam is itself a direct contravention of the religious beliefs of billions of others, just like Jesus being the Son of God in Christianity is an affront to millions of Muslims. There is thus no way of protecting religion from blasphemy without actually banning the very expression of religious beliefs themselves.
