For example if centralized exchanges are discriminating then we should solve the actual problem by either replacing CEX with DEX or adding more CEX that don't do the same thing maybe in other jurisdictions so that those CEXes that discriminate lose business and lose enough money to either have to shut down or be forced to change their rules.
We can add as many DEXs as we like, but if people continue to be happy to sacrifice their privacy and security to centralized exchanges then it achieves nothing. We need to move the users, which is a very difficult thing to do. And if you want CEXs to stop spying on you then you need to stop the government from demanding that CEXs spy on you or be shut down, and you'll have an easier time brute forcing Satoshi's keys than you will convincing the government to stop their mass surveillance programs.
1 bitcoin is always 1 bitcoin whether it is virgin coin, mixed coin or a "regular" coin when you want to use it as a currency not in some centralized service like for trading.
At the moment, maybe. But at any point, merchants/traders/other users could decide that cashing out "tainted" bitcoin via an exchange is too much of a risk and so they will only accept "clean" bitcoin.