Islam contains a vast landscape of ideas and schools of thought.... Each school has common and different views on the practice of Islam. All recognizing the Koran as the supreme authority with varying views on the Hadith etc. etc.
I have had extensive friendships with Muslim people. One dear friend asked me to travel to Istanbul which I did for a month. All I had to pay was the travel expenses. When I offered to pay , I was refused (I felt obliged to at least offer to pay ) according to their custom. Knowing that to persist would cause offense ,I explained myself and let it go. I had a guide throughout my time there and went to many places nonmuslims would not venture to go. These travels ,my friendships, meetings and study have profoundly affected my understanding.
My library has many books on Islam from different perspectives. A number of those books where purchased when I was a regular attendee at Friday Islamic meetings while attending the University of Florida. Funny enough when I went to UMass Amherst, a Muslim friend of mine asked if I would teach his group about Said Nursi as I became very familiar with his teachings due to the previous meetings. This was brought about through my discussions with him on many matters of his faith and practice.
A good portion of my knowledge concerns Sunni Islam, Sufism in particular, but I have had contact with those who are Shia (which many Sunnis consider to be false even outside the faith) and examined their history and practice as well . I write this to say there is much to know and understand and encourage everyone here to examine the facts carefully.
To become a Muslim requires the belief /proclamation of the Shahada which is to say there is no god but Allah (God is one) and Mohammed is His Prophet or messenger..
Concerning Romans 12 20 the verse is pointing to one of a number of consequences for the enemies of the Christian faithful. The primary command is to love your enemies. A consequence of this is if one's enemy persists in his or her attitude, then such a person will suffer a greater judgement. The other consequences written elsewhere includes that by a Christian's testimony of faith and good action the offending party might come to the realization of the sincerity of the believers faith and behavior and either come to faith or change his or her attitude/actions etc. . Reading one quote without the knowledge of the total picture merely distorts the message. The same could be said of Islam . But there are major differences between Christianity and Islam. One should not be blind to the potential problems as well.
As to interfaith meetings ,I have been to a number of these events. Most if not all where sponsored by Gulen's movement or those inspired by his reaching out to other communities of faith etc. . The same Gulen who Erdogan wants extradited for charges of treason among other things. The fued between them had grown through the years,but that is a different story.
Q