The Right to Lie: Google’s “Web Environment Integrity” Proposal is a Geyser of Badness Threatening to Swamp the Open Web.
If your computer can't lie to other computers, then it's not yours.
This is a fundamental principle of free and open source software. The World Wide Web abides by this principle, although we don't often think of it that way. The Web is just an agreed-on set of programmatic interfaces: if you send me this, I'll send you that. Your computer can construct the "this" by whatever means it wants; it's none of the other side's business, because your computer is not their computer.
Google's so-called "Web Environment Integrity" plan would destroy this independence. "Integrity" is exactly the wrong word for it...