The implied meaning of the word "anti-Semitism" is "opposition to anything Semitic", Semites being the people descended from Shem (mentioned in the Bible). To this group belong, among others, Jews, Arabs, and Assyrians. The original meaning of the word "anti-Semitism" was not "opposition to anything Semitic", but the specific form of "hatred of the Jews, as a race", as it existed in Europe for many centuries.
The reasons for this hatred of the Jews by the Europeans were religious, racial and social.
The religious causes of anti-Semitism go back to pre-Christian times, and consist of the resentment of the European pagans (idol-worshipers) at the refusal of the Jews to worship their idols and to follow their social customs.
The Christians were European pagans, who accepted the Jewish Bible and the teachings of a Jew, Jesus, whom they believed to be the Son of God. The Christians blamed the Jews for the killing of Jesus, and saw them as the people damned by God for the murder of His Son. Such Christian views of the Jews persisted as the official doctrine of the Roman Catholic Church until 1965, when the Vatican accepted the legitimacy of Judaism as a religion and exonerated the Jews from the blame for the murder of Jesus.
The religious anti-Semitism was compounded by the fact that Jews had different racial characteristics from most Europeans, which made them fair game for racist attacks.
But in spite of the oppression and segregation to which the Jews were subjected in Europe, they were succeeding to place themselves into positions of economic superiority, by engaging in banking, money-lending, and other business activities. This excited envy of the Europeans and was the social cause of anti-Semitism.
At the end of the 19th century and during the 20th century, as Christianity was being increasingly replaced by political ideologies, pseudo-scientific racial theories began to emerge. The term "anti-Semitism" itself appeared at that time. This pseudo-scientific anti-Semitism culminated in the Nazi anti-Semitism and the Holocaust (a mass extermination of Jews).
There was no "anti-Semitism" in the Muslim world - racially the Arabs themselves are Semites. Religiously, the Jews were seen, as the "people of the Book", and were treated with tolerance. The current Israeli-Palestinian conflict is neither racial, nor religious, nor social - it is geo-political. It is the result of the displacement of Arabs from the coastal Palestine, which is the present state of Israel, in 1947-48 and of the subsequent further Israeli expansion after 1967. These displacement and occupation did result in hatred of Jews by the Palestinian victims of these acts, as well as by all those sympathetic to the victims. But among Arabs and Muslims this is not the old "European Christian anti-Semitism", but hatred of a victim of injustice towards the oppressor, similar to the hatred of the colonized people of Africa and Asia towards the European colonizers at the time when much of Africa and Asia was under European colonial rule. But the Israeli governments and their supporters called this hostile attitude of Palestinians and their supporters towards the State of Israel "anti-Semitism", seeking to conflate it with the old "European Christian anti-Semitism" so as to get US and European support. By saying "they hate us because they hate Jews (like European anti-Semites did before)" they were hiding the real cause of the conflict and vilifying Palestinians and their supporters in the eyes of Americans and Europeans. This, however, did not prevent some people in US and Europe and even some Jews in Israel from seeing the truth.
As the Israeli policies towards the Palestinians began to provoke criticism of these policies in the US and Europe, the Israeli government and its supporters started to use the word "anti-Semitism" to describe any criticism of the Israeli policies. And this is even when such criticism came from Israeli or Diaspora Jews.
Following the events of the 9/11 (2001) in New York, the US government has proclaimed a "war on terror", which had become the defining factor in the national and international politics of the 21st century.
The ideas underlying the War on Terror doctrine, did not appear in 2001, but go back to the early 1980s when Benyamin Netanyahu (the current Israeli head of state) sought to present the Palestinian resistance, as a threat not only to Israel, but to the "West" (USA, Europe, Canada, Australia), and thus to mobilize the US military might to crush this resistance by effecting "regime changes" in all Arab and Muslim countries supporting the Palestinian resistance. In addition to promoting his "War on Terror" ideas in books and speeches, he also inspired a multi-faceted activity by a variety of pro-Israel groups in the USA and Europe to establish control of the Government and of the Main Stream Media, and to use them in support of the Israeli policies. The results of these preparatory activities came to full view only in the 21st century, when the War on Terror has revealed the extent of Israeli influence on the US and European governments.
But, in spite of the massive support by the pro-Israel Main Stream Media in the US and Europe, the War-on-Terror wars, and the policies pursued by the Israeli governments in the 21st century have resulted in substantial and growing popular opposition. This opposition has been further strengthened by the deterioration of the economic conditions in the US and Europe. And while this opposition is to the policies of the US and European governments, there is a growing general public perception that "Jews as a race", rather than "a group of political manipulators some of whom happen to be Jews" have too much control over the Western governments. And this has resulted in a growing hate towards Jews, as a race, similar to the old-style European anti-Semitism.
There is, however, a difference between, the "old" anti-Semitism and the "new" one. The old European anti-Semites hated Jews for what they were (an immigrant racial and religious minority among the dominant native majority), the new American and European "anti-Semites" hate the Jews for what the Israeli government and their supporters in the US and Europe do: oppression of the Palestinians, lawless wanton wars justified by false arguments, domination of their governments and media. And pro-Israel propaganda presenting the New Anti-Semitism as the old one, still further increases the hatred of Israel and of its supporters.
The pro-Israel groups are aware of the growing unpopularity of Israel and to counter it they initiated "Advocacy of Israel" activity on the Internet. Groups of "Advocates of Israel" are posting messages in various blogs, discussion forums and comments on articles published on media web sites (CNN, alJazeera, etc) to "argue their case". This, however, yields results opposite of those intended - increase of anti-Israel views.
The State of Israel was created to put an end to the Old European Anti-Semitism. But having created this state on land owned by other people has produced a new hatred of the Jews, this time not limited to Europe, but all over the world.
By creating the State of Israel the "International Community" (USA/Europe) hoped to resolve the European Jewish Question, but this has created a Palestinian Question. And failure to resolve this Palestinian Question is reviving the Jewish Question on a global scale.
The only way to put an end to this growing New anti-Semitism is to abandon Netanyahu's War-on-Terror and to resolve the Middle East Conflict non-politically - on the basis of Justice. And, as this will not only achieve justice for the Palestinians, but will also achieve Netanyahu's dream, he could use his influence over the US and European governments to guide them onto the Right Path, rather than pushing them into the abyss of another war.