Muscatine

If you can point out a sizeable group of christians, that within the last several hundred years, killed people of an opposing culture or religion, because of and, in the name of their own religion, I will side with you.  

Would the Catholic Irish and the Anglican English killing each other over the past 4 or 5 hundred years count?  They've only tapered off in the past few decades.   Cromwell killed entire towns.

Would the Protestants and Catholics of Germany killing the Jews throughout Europe count?

Would the Mormons killing a small band of settlers passing through Utah count?

Would the Spanish Inquisition count?

Would Catholic Cortez doing away with the natives of Mexico who would not convert count?

I realize the last two might be outside your time frame.

No, these groups are not "sizeable" when compared to the muslim population. 

This is one of your problems.   You lump all Muslims into one group.   They're not homogeneous.  It's tough to find another "sizeable" religious group that large so you've made our task impossible. 

Cromwell died in 1658.  The Irish/English conflict was not about religion, but about sovereignty.

Cromwell died but the killing went on until a few decades ago.    And still is sporadically.

Tell a Catholic Irishman it wasn't about religion and he will quickly set you straight.   It continued long after Ireland gained its independence.

The killing of the jews was promulgated by a comparative limited number of people. 

Compared to 2 billion muslims, of course, but still "sizeable".

It wasn't based on "scripture".

Didn't "scripture" define the two groups?

Mormons? Spanish Inquisition?  Cortez?  You'll have to do better than that. 

You can ignore these if you wish but deaths because of religion happened.