While Herzl claimed that the establishment of a "Jewish" state would cure anti-Semitism, he also promoted anti-Semitism to further his cause.
Herzl stated in his diary
“So anti-Semitism, which is a deeply imbedded force in the subconscious mind of the masses, will not harm the Jews. I actually find it to be advantageous to building the Jewish character, education by the masses that will lead to assimilation. This education can only happen through suffering, and the Jews will adapt. ”. (From his Diary, Part I, pp. 68)
While it is true that Herzl made such a statement, the question is when he made it. Hertzel initially believed that the only cure for antisemitism was assimilation. However after the Hertzel witnessed the events of the Dreyfus affair in 1894, and the antisemitic Karl Lueger's rise to power in 1895 he came to the conclusion that the only way to truly avoid antisemitism would be to create a Jewish State.
According to Wikipedia
It was the rise to power of the anti-Semitic demagogue Karl Lueger in Vienna in 1895 that seems to have had a greater effect on Herzl, before the pro-Dreyfus campaign had fully emerged. It was at this time that he wrote his play "The New Ghetto", which shows the ambivalence and lack of real security and equality of emancipated, well-to-do Jews in Vienna. Around this time Herzl grew to believe that anti-Semitism could not be defeated or cured, only avoided, and that the only way to avoid it was the establishment of a Jewish state.(1)Contrary to the TrueTorahJews belief that Zionism is the cause of world wide antisemitism, the truth is that not only did antisemitism precede Zionism by thousands of years it also led to the formation of the Zionist movement and the push to create a Jewish State in Palestine.
A simple study of Jewish history throughout the years would reveal that no matter where the Jews lived they suffered. The Jews flourished in Babylon until they were oppressed and forced out. Thousands of Jews were butchered during the first and second crusades. The Jews thrived in Spain until they were forced to convert, kicked out or slaughtered during the Spanish Inquisition in 1492. Tens of thousands of Jews were viciously murdered during the Khmelnytsky massacres in 1648 (T'ach V'tat). And then of course there was the ultimate explosion of anti-Semitism that resulted in millions of Jews being killed during the Holocaust.
A fact that one should be aware of is that Theodore Herzl was raised completely secular in an assimilated family. He had no connection whatsoever to Torah Jewry. This detail must be taken into account before attacking him for his secular "anti-Torah" beliefs. For someone so removed from Judaism as he was to come and suggest the Jews build a national home for the Jewish people in Palestine is pretty remarkable taking into consideration his assimilated background. He literally devoted his entire life to the cause bankrupting himself in the process. If anything Hertzel should be praised for his tremendous mesiras nefesh instead of being criticized and denounced by the Torah world. In his zechus thousands and thousands of secular Jews moved to Palestine to build up the Land and pave the way for the rebuilding of Torah that was lost to the land for thousands of years. In his zechus Eretz Yisrael is now the Torah center of the world. We may not agree with the secular visions of Hertzel or the anti-Torah attitude of many of the secular zionists who came to build up the land after thousands of years of desolation but at the same time we have an achraius to recognize the long term good for klal yisrael in Eretz Yisrael that his vision created.
(1) Kornberg, Jacques (December 1, 1993). Theodor Herzl: From Assimilation to Zionism. Jewish Literature and Culture. Bloomington, Indiana: Indiana University Press. pp. 193–194 as seen in Wikipedia entry Theodor Herzl