We do have a duty to spread the Message, it is up to them to if they want to follow it.
3:20 If they argue with you (O Messenger), tell them, “I have submitted to God; I and those who follow me.” Say to the People of the Scripture, and to those who have no Scripture, “Would you submit (to God)?” If they submit, then they have been guided but if they turn away, then your duty is only to convey the Message. God is Seer of His servants.
3:21 Those who reject the messages of God, and wrongfully kill (degrade) the Prophets or their Mission by mixing truth with falsehood, and kill or harm the advocates of justice in the society; promise them grievous retribution.
I would like to ask all learned members of the forum to go on youtube, facebook etc and present the Quranic message whenever you come across the lying hands and tongues of the scribes. Just quote relevant Quranic verses but try not to get too involved in the "F..." responses you may get, rise above this. I particularly enjoy quoting the Bible to anti islam christians!