"Your behavior is not acceptable" and send him to another room -- that was the advice of our psychologist regarding my 5 yr old's out burst. It's purpose is to remove the disruption from the family. And over time, he is supposed to realize inappropriate behavior results in him not being with the family. This is new for us. I have a SN 5 yr old so our circumstances are slightly different, he has verbal communication understanding problems and needs something other than verbal to comprehend right from wrong.
WOW, 4 is young for back talk. I didn't get this until age 7 1/2 to 8 with my oldest and it is a nightmare, he's 9 and we're still getting it and it seems to be worse at times. Sometimes stuff I try works and then sometimes the same thing I do, does not work.
What I've tried:
- since my son is 8 I've tried talking to him about it, not so easy at 4.
- I put my hand up, I say "stop, you are not talking to me in a manner that is nice, let's start again, nicely". If I can get him to stop, this works, sometimes he is in his own little tangent and it does not work. Or he gets frustrated w my stopping his train of thought and then gets mad. Which tail spins out of control, he jumps up and down throwing a fit of rage and it's impossible to "reason" with a child when they are like this. I will walk out of the room or send him to his depending on the particulars.
- rewards for a positive day
- taking away tv & video game priviledges
There is only so much taking away I can do before it become non-benefical b/c he's aways without it. I try to limit the take aways to 1 to 2 days otherwise it's not an incentive to listen to mommy and respect adults. I will say this is not my first line in modifying behavior. I take away things after I do not get cooperation with allowing him to try again of if he pitches a royal fit (which happens and it nearly boils my blood and it takes a lot of self control not to ground him for life LOL I'm only human).
Kids know what buttons to push on you and they learn it early. The key is to untrigger that button for yourself, it isn't personal. My dh tells me this all the time, it is starting to sink in.
When my 5 yr old yells that I'm a stinkin' poopy mommy for sending him to his room, I breathe, it isn't personal. I don't like being called names, but the battle isn't the name calling it was the hitting or other physical behavior he is known for that cause me to say "your behavior is inappropriate, go to your room for 5 minutes of quiet". Amazingly, I only had to carry him to his room a few times the first day I used this technique, now he goes on his own telling me I'm a poopy mommy.

: He's SN, it isn't personal...
I have 4 children and with each I wonder who is going to act up. This last time it was my oldest. Crying I didn't love him anymore, the he never gets attention b/c I'm always doing things for the littles (they were nb, 2 and 4 then). I felt horrible and I had been so sick pregnant and had really relied on him for things normal 8 yr olds don't do - like fixing breakfastes and lunches for his brother and sister, I was too sick to get out of bed until late afternoon.
I think taking special time out for the new sibling to be is important. I have given all the children a gift with each new baby and they give a gift to the baby (my dh takes them to pick something out). We started this with our first to entertain him in the hospital w the 2nd being born via c/s. Anyway, the gift I gave them for the birth of my dd was new PJs, so it does not have to be lavish. They wore those matching PJs for pictures w their new sister who was born at home, it was very cute.
Anyway, as a seasoned mom, I would definitely say you are right on about most of this being baby related. It gets easier. My oldest being able to tell me his fears was really shocking. I never thought in a million years he thought we wouldn't be able to love him in addition to a new baby. It was a very sad moment for me, I had to go around and show him that the only baby picture on my dresser was his (by default of the fact I'm too busy to add the others, but I thought it would help me feel more special).