But in so doing, they established a precedent for removing parts of the supreme law.
I don't quite understand your reasoning there. The whole point of the process of amendment is adding to or removing parts of the supreme law. It was necessary to pass an amendment because enacting prohibion would have been unconstitutional without it.
And my point was that the amendment itself was unconstitutional, regardless of what the majority of the states or people wanted. It infringed upon the 'pursuit of happiness' (property rights). As i stated a bit ago,:
"The prohibition of the sale of intoxicating liquors in the United States was repugnant to the supreme law which protects private property and the disposal and sale thereof."
I will always be of the opinion that even if everyone in the country voted that it is illegal to sell cream soda, it will still be my right to do so.
As far as your point in removing parts of the supreme law, that's a 'no-no.' We can add to the constitution as long as what is added is in pursuance to the rest of it. But we cannot remove roadblocks to insure pursuance.