The difference is that Catholics are not murdering people in the name of Jesus. And if they are, there is nowhere in the New Testament that supports it or says they can murder their way into heaven.
Exactly. With the exception that it's not "if", but WHEN they, and Protestants too, did in the DISTANT past (and as brutally as Muslims ever did) it still was not justified by Jesus's teachings. Therefore, the power of Christ Himself did, and continued to, provide correction - a correction power Islam does not and will not ever have. The proof is that from out of those times, Christians created the Constitution and the 1st Amendment, while Islam is no different - if not worse, seeking to kill America BECAUSE OF it's protection of freedom.
It must be remembered that there is no love at the core of Islam. I don't think people realize how unconsciously dependent they are on that single concept - it's literally the root of what we conceive of as the core meaning of religion itself. It's why we feel safe having a non-specific 1st Amendment, that applies itself to no particular religion.
If the Founders made a mistake it was in not declaring Islam a non-religion for the meaning and purpose of the 1st Amendment. Islam is a terrorist political organization hiding behind religious freedom, and before the problem they represent is solved, the 1st Amendment definition of "religion" will be acknowledged as excluding them. This WILL happen, because its the truth and it MUST happen for America to survive this demonic enemy that fundamentally rejects EVERYTHING this country stands for.