The only thing that happens when you sue FB over patents is that your patent grant covering React is gone, reducing your license to a regular BSD license. If you use Angular, vue or whatnot open source products covered by licenses without patents grants, there is NO guarantee whatsoever that this piece of software is free from patents of Google, FB, Oracle your favorite patent troll from around the corner. Yet people seem more fine with using software which comes without any patent grants whatsoever, and declare that hell would come over us if the FB patent grant on the software would be revoked.
Btw, clauses that revoke patent grants when you sue a party are pretty regular and present in the Apache License v2 and the (L)GPLv3, no one is crying about it and says that those licenses are not open source anymore. The GPLv3 goes even further and invalidates your right to use the software at all if you start sueing people who created that software.
Gosh, I am so happy to live in the EU where we do not have to deal with this kind of BS and can just use the best technology that solves the problem.