Being a false prophet and another liar to defeat must be done in accordance with the teachings of the Quran:
22:40 Those who have been evicted from their homes unjustly, for no reason other than saying, "Our Lord is God!" (They should remember) if God had not enabled some people to repel others; temples, monasteries, churches, synagogues, and mosques, where the Name of God is oft mentioned, would have been destroyed. And God will certainly help those who help Him. For, God is Mighty, Powerful.
22:41 They are the ones who if We give them power in the land, establish Salaat (the Divine System), and set up the Just Economic Order (in which wealth circulates freely to nourish every member of the society, and the basic needs of all individuals are taken care of). They promote the Permanent Moral Values and discourage what the Qur’an forbids. And in their governance all affairs are decided according to God's decrees (given in the Qur’an. 5:44-47).
16:125 Call to the way of your Lord with wisdom and sound exhortation. Reason with them most decently. Your Lord is best Aware of him who strays from His path, and He is best Aware of the upright.