It is important to start by making a distinction between Christian and Muslim, or Christianity and Islam. That is the distinction in terminology, but more so in its intrinsic belief systems. Having said that, within these major belief systems there are numerous strains of differences in what they would place in their religious practices and expressions. Furthermore, the Christians have a distinct set of "rules" that is applied to who might be the true Christian. The same applies to the Muslims. Within the overall religion, there are many extremists, and "sects," that would stray away from what Islam teaches.
Christianity revolves around the teachings of the Bible and accepting Christ as the Lord and Savior. The word "Christian" was first used in the time after Christ's crucifixion, and ironically, the period when these Christians were persecuted as well. In the "true" Christian circles, anyone who does not adhere to accepting Christ into his or her life, and living by the teachings of God's Word is not a Christian.
However, Church History and people in general (in the twenty-first century) regard a Christian as anyone who hints at attending church and use the Bible as their guideline. Those, though, who have accepted the above definition of "Christian," would frown upon those who do not accept this as part of their lives. Examples of such Christians are those who call themselves Catholics, Anglicans, Yazidis, Ahl-e Haqq, Mandeans, Shabak, and Bahai. Many of the churches formed from the outcome of the Protestant Reformation would also be included in this group.
Hence, there are certain belief systems that would silence the Christian world about the persecution of the Christians in Iraq. Firstly, most of these Christians are Yazidis. Who are the Yazidis? They are a religious minority that has a religion based on a mix of Islamic beliefs, Zoroastrianism, and Mithraism. Under normal circumstances, the Roman Catholics and the Anglicans would deem these Christians as non-Christian. However, they are regarded by ISIS (the Islamic State of Iraq and Syria) as Christian, and, therefore, to be eliminated and executed.
Within this context, there is a call for intervention against the persecution of Christians. Again, it is difficult for the "true" Christian to support them in prayer or any other means of assistance as they do not believe that these are true Christians. For this reason, not much is being said or done about this on the scale of the Gaza massacres.
The point of this story is to awaken people to do just that. Human beings are being slaughtered (true or not), and as Believers in Christ, which makes you a true Christian, you should intervene in any way possible. Many other "Christians" are being killed "in the name of Allah," and most ordinary, loving Muslims are against such killings. We should, therefore, pray for one another, whoever we are and wherever we are.