It is not a parent's job to respect their children. And often the biggest problem between parent and child is that the parent can't actually see the person that their child became. Here's your reality, you are disabled. You are limited in the activities and chores you can do. He forgets that and only remembers that he's the parent who always told the child what to do and he keeps returning to that. You are not supposed to get respect from him but you need to sit down with him and explain to him what your limitations are and that you are unable to do that chore and some others because of the back problem. I'd also suggest that you find something you can do to share in the household responsibilities, and talk with him about what you can do to help out.

It is not his generation - don't get into the mindset. He simply sees you as a kid that may be trying to get out of doing work - likely because that's something you did as a kid. One thing people have difficulty with is dealing with an illness that isn't visible - I've got a chronic illness and suffer pain and sensitivity continuously - I've had to remind even my closes friend of my limitations every time we try to do something - they just don't seem to remember, and I'd venture to guess that's what your dad is doing - you don't look sick to them, so you mustn't be. He's feeling put out and needs help, so see what you can come up with. You need help and so does he - he obviously feels burdened and that's why his ranting.