To play Devil's Advocate for a moment, don't people on the outside say the same thing about Christianity?
Atheists and agnostics always critique the Bible for having two different Gods, the Old Testament God who commanded genocide, and the New Testament God who commanded love of neighbor. Obviously we know the two are consistent, but to someone picking up the Bible for the first time, the Pentateuch and the Gospels almost appear to be from different religions.
I wonder if there is similar nuance within Islam that I, as an outsider, don't know all the details of. Kind of like how ex-Christians often assume all Christians are basically Protestant evangelicals. We're not, there are so many gradations of doctrine and practice. If Islam had some similar internal disagreement, I wouldn't necessarily know about it any more than the secular guy would know about all the disagreement within Christianity.
You often here non-Muslims repeat the same talking points about Islam, but I want to be careful not to paint with too broad a brush.