Books about anti semitism are propaganda, though the word itself can be applied pretty broadly, especially today when people are hyper aware of the nature of propaganda. Books advocating the hatred of any race, religion, or group of people are an attempt by the authors to sway the opinions of the public.
Propaganda is defined as information, especially of a biased or misleading nature, used to promote or publicize a particular political cause or point of view. Therefore I believe books that uphold anti-Semitic topics obviously fall into this category. I believe we should implement a system that helps label books as propaganda or biased.
Books on the topic of anti-Semitism should not necessarily be considered propaganda. Although they might be offensive or racist, they might not necessarily qualify as a message of propaganda. Books on the topic might be neutral, objective statements about the existence of anti-Semitism in history or about efforts to stop it.
As far as I know, the Constitution of the United States allows for the right of free speech. I do not think that books that are considered to be anti-Semitic should be considered propaganda because it puts them under a label that makes them more likely to be banned. I cannot speak for others countries, but for my own, there are certain things that I don't want to hear or see, but I do not believe in throwing labels on them just because I don't like what they say.
If anti-Semitist books are propaganda, then everyone's opinions should be labeled as such. Propaganda is the telling of lies to push a political agenda. Anti-Semitism isn't necessarily a political stance, just racist people who have a strong opinion. Until anti-Semitic people turn violent and kill someone else for their believes as a hate crime, they are entitled to their opinions.