What makes the patent grant unfair? I think saying "you can use our pretty powerful technology until you sue us" is a great way to defang the patent system.
For a more balanced approach to patents, see the GPL, Mozilla Public License, or Apache 2.0 License.
He doesn't agree with your interpretation. The license is very clear in that everything a company would typically do to /defend/ against a patent suit brought by Facebook will terminate its patent rights on React.
Let me quote the second paragraph (added line formating for readability), the (b) part is the broadest I think:
The license granted hereunder will terminate, automatically and without notice,
for anyone that makes any claim (including by filing any lawsuit, assertion or
other action) alleging
(a) direct, indirect, or contributory infringement or
inducement to infringe any patent: (i) by Facebook or any of its subsidiaries or
affiliates, whether or not such claim is related to the Software, (ii) by any
party if such claim arises in whole or in part from any software, product or
service of Facebook or any of its subsidiaries or affiliates, whether or not
such claim is related to the Software, or (iii) by any party relating to the
Software;
or (b) that any right in any patent claim of Facebook is invalid or
unenforceable.
It says making "any claim" against a Facebook patent will terminate your right to use the software. Facebook gets to protect its own software patents: "that any right in any patent claim of Facebook is invalid or unenforceable."
The other lines are okay, it seems.
I am not an IP law expert or lawyer though, but the writing seems pretty simple.