While there have been in fact wars based on religion, throughout history these only represent a fraction of the total number of recorded wars (source: http://www.foreignpolicy.com/articles/2012/08/06/god_and_the_ivory_tower?page=0,2#sthash.677b3S2j.dpbs) The current civil war in Syria is not of a religious cause but a revolt against an oppressive government following greed. Most if not all religions in their purest forms condone peace and tolerance (including the three Abrahamic religions, it is man and extremism that distort the words. In conclusion yes freedom of preaching should be a right BUT without going to the extremes.
All the violence we have been seeing in the Middle East is being carried out n the name of religion and according to certain interpretation of Islam and Judaism. In the name of Islam, people are being slaughtered in Syria and most of the Middle East. In the name of Judaism entire country (Palestine) was occupied and its people were uprooted from their homes.
It is certainly difficult to articulate in a fashion that will accommodate the sensibilities of theistic readers, but I will try. With any free speech, any freely expressed idea, the speaker has a duty not to inflict harm directly, not to impose when unwanted, and certainly not to effect, by his speech, a situation where there is clear and present danger of harmful ramifications. That is the bargain.
First, the duty not to inflict harm. I argue that by teaching religion, and especially those aspects of religion which directly oppose prevailing scientific theories, preachers and other theists are sabotaging children's capacity to think and reason for themselves, and to compete on a level playing field with properly educated and prepared children. Effectively, religious "teaching" is a devious and permanent mental handicap. It should therefore be strictly curtailed. If a person chooses, later in life, after attainment of a sound mind and personal identity, to explore religion and indoctrinate oneself within, that is absolutely permissible, but please stay away from the children.
Second, not to impose when unwanted. Some sects send people to your door in the morning. Some sects take the long way around and try to preach in your children's schools, or contribute to your congressman's campaign. In each case, the contact is unwanted. Simply stay away, and preach to the willing.
Third, clear and present danger. Yelling, "FIRE" in a crowded theatre is one well-trodden example. I argue that religious preaching is too similar. Christianity, in particular, yells that very word, "FIRE and brimstone," to scare and cull the masses. I argue this is emotional and psychological abuse at best, brainwashing at worst, and should be banned outright unless the church can provide hard proof that its claims of an afterlife exists. Otherwise, my arguments from the First point become valid here as well. People subjugated to these unsubstantiated fallacies are mentally and spiritually crippled, and coerced into membership and action that they would not otherwise desire, were they not subject to these scare tactics. Other members of society suffer collaterally as well, as perfectly upstanding members of other religions, or people of varying racial and sexual identities, and social sensibilities, are ostracized and criticized and forced to defend themselves in the public eye against a wave of hatred and intolerance.
If religious speech can avoid these three conditions, then by all means I shall condone it. Until such time, keep it in the church.