When he served as America’s minister to France in the mid-1780s, Jefferson had once confronted an Arab diplomat, demanding to know by what right his country attacked Americans in the Mediterranean:

The Ambassador answered us that it was founded on the Laws of the Prophet, that it was written in their Koran, that all nations who should not have answered their authority were sinners, that it was their right and duty to make war upon them wherever they could be found, and to make slaves of all they could take as prisoners.

And people want us to be more tolerant of a religion that swears to make slaves of all who don't do what Muslims tell them to.  Some people just don't read deep enough.  Something else of note was said by a Republican senator in response to this event:

“The Prophet Muhammad inwardly heard the Arabic verses of the Koran. He did not simply encounter the Divine Meaning and compose his own words to express it. Therefore, no translation of the Arabic Koran into any language can be the Holy Koran, but is simply a human interpretation, which may be inspired but does not exist on the sublime level of revelation.” So, technically, he’s not swearing on the Koran.