It depends on how you define "freely". Christian children were stolen from their families in the time of the Ottoman Empire and were forcibly converted to Islam, trained as Janissaries, and then turned around and sent back to persecute their relatives. That's one teeny, tiny example. I can pull up thousands of other incidences of Muslim persecution and genocide against Christians, like what happened to the Greeks and the Armenians, Or what's happening today in the Muslim world. Or Islam's spread by the sword during its early days among now-formerly Christian lands in the Middle East, North Africa and Asia Minor.
If anyone at all turns up dead anywhere in the Muslim world, one shout of "Christians did it!" sees dozens of Christians either savagely beaten or killed, Christian homes and businesses burnt, and churches desecrated.
And let's not forget that a Muslim converting to Christianity in an Islamic civilization faces the death penalty for "apostasy", and the Christian community with which the ex-Muslim now worships also faces severe retribution from the Muslim authorities.
So sure, we Christians are allowed to worship freely--that is, quietly within our own homes and churches, far away from any Muslims who might see the truth and beauty of our religion, and who might be tempted to leave Islam for Christ. We are most certainly not allowed to proclaim our faith to the Muslim community at large (unless we do so at the executioner's block, that is), or to convert anyone else under Islamic law.
At least our religion doesn't teach us to fight the non-believers, and instead teaches us to turn the other cheek, pray for those who persecute us, bless those who curse us, and do good to those who hate us. So any Christians who ARE ruthless and bloody are going completely against what our religion teaches.
Oh great, one man who fought against the Crusaders, who were hated by Muslims and Orthodox Christians alike. That's your great proof that Muslims were always nice to Christians?