I have been watching Emmerdale since 1972 ,its been my all time favourite show and have seen many times when Jack beat people up and hit his son ,so I believe for a change what Robert said ,Jack most likely did give his son a hiding for being gay and if you watch the clips others have shared on this site you will most likely understand why It is likely that Jack did this when Robert was younger . Go look at the thread.......
http://forums.digitalspy.co.uk/showthread.php?t=2184960
http://forums.digitalspy.co.uk/showthread.php?t=2184960