If "we" refers to Americans, (and I can't read the original post, so I'm just assuming the obvious) then the poster is right. It's pretty common knowledge that a significant number of people stolen from West Africa were Muslims. (So-called) Americans might not have been the FIRST to take away their freedom, but once in the US, they remained slaves.
There were no Americans in the 16th and 17th centuries. The African slave traders were mostly Muslims. What you consider to be "pretty common knowledge" must be PC public school indoctrination, because it certainly isn't history. Jumping in to the debate without reading the "original post" is not helpful.