I don't know when you grew up but for a long long time kids have uttered phrases such as that. In the past it was much more acceptable (we didn't necessarily know the damage or it wasn't as widespread given attention) for an immediate physical reaction. I grew up in the belt across your butt was viewed in a different light for example. Unfortunately you also have hit (no pun intended) upon the note about disrespect because a lot of that comes down to parenting styles. Disrespect doesn't mean the same thing to others. For some their line is a lot further away in the sand than others.
I'm not sure you should be glad because you lived under the threat of physical action should you have stepped out of line, maybe that worked for you, but it's far from a psychologically safe place as a base line for childhood development although again as I mentioned I must give attention that for certain cultures and ethnicities things are viewed differently.
I said you could imagine not that you were hit. "could never imagine saying that to someone that I loved" and I replied that while you couldn't imagine that, you could imagine being hit by your parent should you have said that ("if I had dared tell my mom to shut up or that I hated her, I probably would have been popped in the mouth."). My apologies but I'm not exactly finding the reason to be what you saw in movies. While I could be incorrect you may have grown up under the understanding should you have said something that to your parents was so severe, to them, that an equally severe reaction would have been likely to occur. I don't know what movies you are watching TBH. Regardless I just found the more nonchalant way physical was handled in comparison to the I hate you/shut up part to be lopsided but understand a YMMV applies here