Examples of Islam's founders striking women

From Sahih al-Bukhari and Sahih Muslim, the two most canonical hadith collections:

Sahih al-Bukhari, Volume 8, Book 82, Number 828:
Narrated Aisha [Muhammad's favorite wife]:

Abu Bakr [first caliph, father of Aisha, and companion of Muhammad] came towards me and struck me violently with his fist and said, "You have detained the people because of your necklace." But I remained motionless as if I was dead lest I should awake Allah's Apostle although that hit was very painful.
Sahih Muslim, Book 009, Number 3506:
Jabir b. 'Abdullah (Allah be pleased with them) reported: Abu Bakr...came and sought permission to see Allah's Messenger...He found people sitting at his door and none amongst them had been granted permission, but it was granted to Abu Bakr and he went in. Then came Umar and he sought permission and it was granted to him, and he found Allah's Apostle...sitting sad and silent with his wives around him. He (Hadrat Umar) said: I would say something which would make the Holy Prophet...laugh, so he [Umar] said: Messenger of Allah, I wish you had seen (the treatment meted out to) the daughter of Khadija when you asked me some money, and I got up and slapped her on her neck. Allah's Messenger [Muhammad]...laughed and said: They are around me as you see, asking for extra money. Abu Bakr [who was later to become first caliph]...then got up went to A'isha...and slapped her on the neck, and Umar [who was later to become second caliph] stood up before Hafsa and slapped her saying: You ask Allah's Messenger...which he does not possess. They said: By Allah, we do not ask Allah's Messenger...for anything he does not possess...
Sahih Muslim, Book 004, Number 2127:
...(the Holy Prophet) entered the (house), and said: Why is it, O 'A'isha, that you are out of breath? I said: There is nothing. He said: Tell me or the Subtle and the Aware would inform me. I said: Messenger of Allah, may my father and mother be ransom for you, and then I told him (the whole story). He said: Was it the darkness (of your shadow) that I saw in front of me? I said: Yes. He [Muhammad] struck me on the chest which caused me pain, and then said: Did you think that Allah and His Apostle would deal unjustly with you?...
Sahih al-Bukhari Volume 7, Book 72, Number 715:
Narrated 'Ikrima:
Rifa'a divorced his wife whereupon 'AbdurRahman bin Az-Zubair Al-Qurazi married her. 'Aisha said that the lady (came), wearing a green veil (and complained to her (Aisha) of her husband and showed her a green spot on her skin caused by beating). It was the habit of ladies to support each other, so when Allah's Apostle came, 'Aisha said, "I have not seen any woman suffering as much as the believing women. Look! Her skin is greener than her clothes!"...

Wife-beating goes on in all societies. Most societies seek to punish it. Islam's core texts and founders, with some limitations, make it into something ordered by God (see the post on Quran 4:34) and thus very difficult to reform.