Man hits infant son on the face, ordered to pay 50 pounds as compensation besides other damages

A baby is very fragile, needing constant protection and care from parents. It is also true that when a baby is born, the hormone systems of the parents push hormones through the body, imparting a protecting emotional feeling (much stronger in the mother), so one wonders what is it that makes a person be able to hit a 10 month old defenseless baby; hard enough that it left a mark on the face and also needed medical attention. Well, the case was as simple as something that babies do, knock things around. The after effects ? The father is now estranged from the mother and the son (the mother and father were not married) and defending himself in court (link to article):

A Briton, who slapped his 10-month-old son after he knocked down a photo frame, has been ordered to pay the baby 50 pounds in compensation, a media report said Thursday. The 24-year-old man lost his cool when his son hit the TV while jumping up and down in his baby bouncer, Daily Mail reported.
Rachel Bentley, defending the accused, said the man was now estranged from his partner and son after the incident, which happened two days before Christmas, and he was "sorry". He was also directed to complete 60 hours of community service, be supervised for a year, deal with his anger management and pay the baby 50 pounds in compensation.