I have heard that Jews have a sixth sense for anti-semitism, but the rest of us must rely upon definitions. At one time, I believed that an anti-semite was a person who hated or persecuted any and all Jews simply because they were Jews. Since then I have come to modify my original belief. I have seen persons accused of anti-semitism for (1) criticizing the policies and actions of the government of Israel. (2) referring to any of a number of examples of racism within Israel. The JNF comes to mind, as well as the unequal treatment of Israeli Arabs. (3) disagreeing with a supporter of Israel in the Haaretz forums. (4) mentioning that Iran has killed far fewer civilians than has Israel. There are lots more. Now I have come to know that "anti-semitism" is a term that can be used by Jews only and it means whatever the user wants it to mean. Mostly it is just used as a perceived insult, although it has lost any sting it may have once had due to over use.
Islamic State militants blow up ancient Arch of Triumph in Palmyra (Reuters)
from the article: EU to give e15 million to college run by allegedly anti-Semitic priest