From the 18th century the Quakers used 'thee' but used it as part of normal modern speech, so there's no 'thou art'. An example:

A Quaker returned home to find a burglar in the house. Picking up his shotgun (used for hunting), the Quaker said: "Thee had better move, my friend, because I am about to shoot where thee is standing."

Emotional and physical violence? I'm surprised. Of course, people can be catty and spiteful, but in my limited experience, Quakers strive to act decently towards others.

I have certainly never heard of a Quaker striking a child; they're absolutely stringent about non-violence - though I suppose it's possible that anyone's temper can snap occasionally.

Here's the Queries, which are at the centre of Quaker life: http://www.stonyrunfriends.org/Queries.html

The new book Chocolate Wars by Deborah Cadbury, about the Quaker families who started the English chocolate industry, has a lot about Quaker living and principles.