- Muslims are using the Shari'a definition of "slander" not the Western one, which means "to mention anything to a person that he would dislike...". whether or not what was said is true.
- Under the Western definition "slander" is defined as " an untruth about another which untruth will harm the reputation of the person defamed." In the West, the truth is an absolute defense against a charge of slander. But not so under the Shari'a.
So the bottom line is this: Muslim groups want to criminalize our saying anything about Islam, which is a gross violation of our First Amendment right to free speech. It's not an issue of saying bad things as it is telling the truth. The Muslims want to remove our right to hold them accountable for the killing of apostates, beating wives, calling Jews apes and pigs, calling for Holy War, honor killings, beheadings, rape gangs, the works. Speaking of such things is a public service, especially when what is said is true.
To reveal such things about Islam is NOT "incitement to hatred and discrimination" per se. But that may be the natural public reaction to the revelations of the atrocities permitted under the Shari'a Law. Such public revulsion may be richly deserved.
 "Reliance of the Traveller" Translated by Nuh Ha Mim Keller, Amana Publications, Beltsville MD, 1991, r2.2 page 730
 https://legal-dictionary.thefreedictionary.com/slander, accessed 12/10/2018