If GPL is superior, do a GPLed fork of LLVM/clang and beat the BSD licensed version with their own code.
You should be able to grow faster.
You have access to their improvements, while they don't have access to yours.
But then you'd be doing what you criticize corporations for, what you fear being done to LLVM by corporations.
You obviously could, but it feels wrong to me. But if it's freedom you are protecting why does it feel wrong?