All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
Orientalists generally attempt to discredit Islam and distort the image of Islam and the Muslims. However, Allaah, The Exalted, prevails in His purpose, although most people do not know. It should be of no surprise that they would do such a thing; Allaah, The Exalted, says (what means): {And thus have We made for every prophet an enemy from among the criminals. But sufficient is your Lord as a guide and a helper.} [Quran 25:31]
This Jewish Orientalist to whom you referred in the question was one of the sworn enemies of Islam and notorious for his hostility to Islam.
It is rather difficult for Orientalists to find a way to criticize the Quran so they attack the Sunnah and the narrators of Hadeeth. Schacht held that the Muslim scholars of Hadeeth and Fiqh found no problem in falsely attributing statements to the Prophet, sallallaahu ‘alayhi wa sallam. He perceived them as a bunch of liars (and that the Ahaadeeth were all fabricated). If this is his opinion of Hadeeth scholars, how could he accept their writings in the Islamic sciences and disciplines?
Indeed, many books were penned in refutation of the Orientalists such as As-Sunnah wa-Makaanatuha by Dr. Mustafa As-Sibaa‘i, Raawiyat Al-Islam Abu Hurayrah by Dr. ‘Ajjaaj Al-Khateeb, Difaa‘ ‘an As-Sunnah by Dr. Muhammad Abu Shahbah, and Al-‘Uyoob Al-Manhajiyyah fi Kitaabaat Al-Mustashriq Schacht Al-Muta‘alliqah bi As-Sunnah An-Nabawiyyah by Dr. Khaalid Ad-Direes.
Perhaps you may find some of these books translated into English. You can also consult its Arabic versions if you are proficient in the Arabic language.
For further information, please refer to Fataawa 8516, 34537, 85821, 107195 and 6956.
Allaah Knows best.