Citation needed. Let's say I have an awesome VR patent, and a React based website. I find out the Oculus violated my patent, what happens next?
Answer: I sue them. :) Nothing about the React license stops this; I will even still have a right to use React. What I won't have is a right to use any patents that Facebook might have on React. But Facebook, as far as is known, has no such patents.
> The license granted hereunder will terminate, automatically and without notice, if you [...] initiate [...] any Patent Assertion
The key part is that if you don't have a license to use the patented technology (or more pertinently - that license is explicitly revoked), you can't legally use that technology, no matter what the BSD license might say: the patent grants supersedes the BSD license.
So, to respond directly to your answer - you lose the right to use React; Facebook can sue you for your use of React, since they own the patents to that technology.
So if you want to operate under the belief that Facebook has no patents to assert, then yes, you will consider yourself to be safe. The fact is that many lawyers, including the Apache Foundations lawyers, disagree with this assertion.
Incorrect. The ASF's objections had nothing to do with believing Facebook had any patents, and many ASF projects are looking to move to Preact, which is presumtively covered by the same patents React would be (if any).
I.e. the exact situation you would be in if you sued Facebook and there was no PATENTS file.
The "implied" license doesn't have a strong legal finding backing it up yet. Even so, most lawyers are comfortable with the idea that if a company tells other people to freely use their software, they can't then come back around and sue those same people.
If you have a patent, and use React, you can't sue Facebook if they use your patent.