One of the things I've recently observed/discovered about kids is how much they mimic/repeat what they see and hear. Now, my kids are older - 8 & 10. However, when I do not speak kindly to my wife, or to the kids, or if I fail to be an example of patience (!!!), I see my kids begin to demonstrate that, too.
It is especially apparent when they come in contact with those younger than they are. I describe this as verbal bullying. What I've observed, in myself and especially on the athletic field, is that both coaches and parents bully their kids around, without even realizing it! "Do it because I said so!"
This is manifest in the form of just saying "No" to a request, or a simple disagreement that warrants discussion. Why not learn to just say "Yes" and then figure out how to get it done. Safety issues, notwithstanding of course.