On the other hand, the Quran contains EXPLICIT language that COMMANDS violence by Muslims against non-Muslims, to spread their faith and or other reasons. People who call themselves "Muslims" and who have employed violence in the name of their religion are doing so in OBEDIENCE of Islamic scriptural commands.
This is a significant difference. The medieval "Christian crusaders", it can be argued, were being disobedient to their faith. The modern Islamic terrorists are being obedient to their faith. Thus, it is legitimate to focus on Islam itself as the issue.
Actually, it depends on what you mean by "new testament" and "Christian." If you are talking about Matthew, Mark, Luke, and John, then what you have said is correct. However, there are are an enormous number of people who call themselves "Christians," but who would be more accurately called "Tarsusians," or "Paulines" [after Saul of Tarsus, or Paul, or whatever you want to call him]. I get in arguments with them all the time here at FR, and, while I try to make the standard points as a matter of duty, I've come to realize that, in general, it's just a big waste of time to try to talk any sense into them.
There are some really ugly proto-Marxist aspects of the post-Christian books of the New Testament.
The Crusaders were fighting a defensive war against mohammedan aggression. They were attempting to defend Christians in Europe and the Near East against oppression. They, unfortunately, weren't successful.