This is the issue I have with boards like this. Everyone is there to point out what you're doing wrong,... but solutions?
Books on common sense and loving ideals are easy to think, write, read, and wholeheartedly believe, however life ican be difficult to live.
Just like SoggyGranola, I can find something wrong with every possible thing to say. THAT is the problem with reading too much!
Finally I settled on what I would say to anyone who spoke poorly to me. (Now, watch this will get lots of responses to your questions...) I respond to sass with an "I do not deserve to be spoken to like that. When you are prepared to speak to me about this with the same amount of loving respect that I speak to you with, then we can discuss this, and find a suitable solution." Now MANY feel that is a guilt card, but I have to take care of my self as well. I put everything out there for the kids. I have to draw the line at being purposely treated poorly. As far as age, only a parent can tell when it's time to be "so harsh". Obviously your average two year old has no idea that they are "being disrespectful and hurtful" to moomy, and saying something like that would be both crushing and utterly confusing, and at the age were discussing (five or so), it is completely up in the air, and quite individual. I have only recently had to say this to my eight year old, who is very capable of understanding the concept. Sorry, but I didn't have the problem at a younger age, so perhaps someone has better advice there...
Hitting: I simply comfort the reciever. I figure that the hitter already feels badly inside, and I do not wish to make them feel ashamed about the loss of control. So I just do the mommy comfort thing with the other child. It seems to have worked out well for us. My boys now seperate themselves before they loose their tempers, and they avoid harmful actions on their own. Yay!