MetaMask is not taxing your crypto transactions.
https://cointelegraph.com/news/metamask-withholding-crypto-taxes-rumor
ConsenSys collects sales tax on certain products/services where they are required to do so by law, and that's not a violation of Web3 principles. Every company that sells taxable products and services collects sales taxes, even if those products and services are paid for with crypto. It's the law. They must collect sales taxes on those transactions by law, and they'd be fools to violate that law as it comes with hefty penalties.
Okay thanks for clarifying that!