yuck. Frozen meat has a different texture and is not a substitute except in emergencies. Though if you are not for cooking yourself you probably have enough other bad things happening in your food chain that you cannot tell the difference.
It's not the chemical structure, it's the physical structure. Slow freezing causes large (relatively) ice crystals, which are more likely to break cell walls than smaller ice crystals. Those broken cell walls result in more moisture loss when cooking, and a different texture when thawed.
[1] https://translate.google.com/translate?sl=nl&tl=en&u=http://...
[2] http://neerlander.nl/2016/09/07/vers-vlees-supermarkt-vaak-o...
agree that requiring all meat to be sold frozen is a step too far though. adding a tax somewhere along the meat production chain to account for the externalities would be a better solution.
But the way humans raised animals prior to the last century seems a lot less problematic. If we reverted to a more sustainable, regenerative practice of farming, that would surely reduce animal suffering and not damage the environment to anywhere near the same degree. It would also create a lot of jobs. But if you're trying to feed 8 bln people then you will need to figure out ways to reduce waste in the supply chain. Like freezing meat.