I grew up in a physically abusive home. Several incidents resulted in police visits.
On one serious occaision, the police had already been informed that the violent outburst occured just after a family bible study. In private, two officers were talking to me and it came out that the family were Jehovah's witnesses. I told them that I was embarrassed to say that because it's not how people should have behaved.
The police said 'You'd be surprised to know how much violence happens in religious homes after family bible study.'
I think people try to behave in such a way to appear religious because they are covering up a true lack of love and honest spirituality. When the pressure to behave and 'appear' a certain way become unbearable, they act out in fits of violence against those who are exposing their flaw(s).