I agree with your stance on aspects of copyright specifically as you point out in the Disney vein.
For me it doesn't hold when an individual or small business invents a unique product only to have their product design stolen and sold at knock-off prices removing any chance they have at reinvesting and continuing to produce additional unique products.
The "don't deny the ladder" argument is still a bizarre mindset. There are lots of laws that come into place after a situation where someone has already made lots of money via exploiting the thing that the law now explicitly prevents. Specifically because the now illegal thing was shown to be wrong.
Some obvious extreme examples:
Child labor, legal prior to the 1900s. Should China be putting pre-teens in factories for 16 hours as well without any guilt because "The US did it while it was bootstrapping."?
Slavery, the United States used slave labor in the establishment of it's economy. Should China be allowed to use slavery?
If your counter argument is, "Well those are humanitarian issues violating individual rights where copyright isn't." then you're just attempting to divide what's considered wrong into "more or less morally acceptable shades of your own making" which doesn't have the effect of suddenly making those more morally acceptable things now acceptable within the greater opinion of humanity at large. Simply put, "Yes, there is scale but copyright infringement is still on the 'wrong' side currently within our society."
If you want to argue that copyright infringement is the right thing to do on the grounds that all copyright infringement is inherently good then I'm willing to accept that's your stance.
If your stance is still, it's "OK" for China to engage in copyright infringement (when you think copyright infringement is wrong) just because the United States did it 160 years ago, then you're holding what to me is a viewpoint based on your own bias towards wanting it to be "OK" for China to engage in copyright infringement and your rationalizing why after the fact.