I'd noticed this New York Times article myself and been somewhat outraged by the same point that Spencer was:
"…A handful of non-Muslim researchers in the West — typically outside the academic mainstream —...[Spencer]: That's Kirkpatrick semaphoring, "Don't take these guys seriously".
... seek to build a case that Islam is inherently more violent than Judaism or Christianity by highlighting certain Quranic verses. But they struggle to explain away approving passages about violence in other religious texts, such as the book of Joshua in the Old Testament, the Book of Revelation in the New Testament, or the statement attributed to Jesus by the Gospel writer Matthew that "I come not to bring peace, but a sword."[Spencer]: Do people like David D. Kirkpatrick ever get embarrassed writing things like this? Do they never look around the world and notice that there are Muslims quoting the Qur'an to justify violence all over the world and not a single Jew invoking Joshua or Christian invoking "I have not come to bring peace, but a sword" to justify violence? And in fact, these "non-Muslim researchers" don't "struggle to explain away" such passages. It's really quite simple. As I have explained many times, both Judaism and Christianity have developed interpretative traditions that for various reasons reject the literal understanding of verses appearing to enjoin violence. Mainstream Islam has not. Nor is there actually any open-ended and universal command in the Jewish or Christian scriptures for all believers to wage war against and subjugate unbelievers; in the Qur'an, there is.
[Me]: read the whole article; it's worth it.