Luther’s statements about Jews go far beyond disappointment and were far more insidious than you are stating. Much of what he said about the Jews would be closer to an Islamic Imam in the Middle East than any Christian leader.
In Daniel Johah Goldhagen’s book, Hitler’s Willing Executioners, he writes:
“One leading Protestant churchman, Bishop Martin Sasse published a compendium of Martin Luther’s antisemitic vitriol shortly after Kristallnacht’s orgy of anti-Jewish violence. In the foreword to the volume, he applauded the burning of the synagogues and the coincidence of the day: ‘On November 10, 1938, on Luther’s birthday, the synagogues are burning in Germany.’ The German people, he urged, ought to heed these words ‘of the greatest antisemite of his time, the warner of his people against the Jews.’”
In brief, dear princes and lords, those of you who have Jews under your rule— if my counsel does not please your, find better advice, so that you and we all can be rid of the unbearable, devilish burden of the Jews, lest we become guilty sharers before God in the lies, blasphemy, the defamation, and the curses which the mad Jews indulge in so freely and wantonly against the person of our Lord Jesus Christ, this dear mother, all Christians, all authority, and ourselves. Do not grant them protection, safe-conduct, or communion with us. . . . With this faithful counsel and warning I wish to cleanse and exonerate my conscience.
-Martin Luther (On the Jews and Their Lies)
As Shakespeare, another child of that era, would remind us:
Shylock: I am a Jew. Hath not a Jew eyes? hath not a Jew hands, organs, dimensions, senses, affections, passions? fed with the same food, hurt with the same weapons, subject to the same diseases, healed by the same means, warmed and cooled by the same winter and summer, as a Christian is? If you prick us, do we not bleed? if you tickle us, do we not laugh? if you poison us, do we not die?