As Adam and Eve were the first human beings, all of us are brothers and sisters
So it does not make sense to fight or kill a human being if someone has different religious faith. It does not matter someone is Muslim or Christian, or Jew or Hindu or Buddhist or Pagan etc., we all are brothers and sisters in a broad sense.
The Quran confirms the common origin of all human beings on the planet. In the Quran God even reveals why He makes different tribes and different religions.
“O people (all world citizens), we created you from the same male and female, and rendered you distinct peoples and tribes that you may recognize one another. The best among you in the sight of GOD is the most righteous. GOD is Omniscient, Cognizant [The Quran 49:13].”
For most of the people, religion is a matter of belief without laboratory confirmation. This is the main reason someone is Muslim but others are Christians, or Jews or Hindus or Buddhists, for example. Therefore, any kind of violence or extremism based on religion is utterly stupid act.
God even does not want that everybody on earth should follow a common faith tradition.
“Had your Lord willed, all the people on earth would have believed. Do you want to force the people to become believers [The Quran 10:99]?”
“Had GOD willed, they would not have worshiped idols. We did not appoint you as their guardian, nor are you their advocate [The Quran 6:107].”
From the light of genetic science even for an atheist, it is an undeniable fact that we all humans are related to each other. Regardless of our religious affiliations, as we all are brothers and sisters we must stop violence and extremism in the name of God or in the name of any particular religion. Thank you and may God bless you.