I have no horses in this race and lack the expertise to judge, but this is part of a larger fight and djb seems to be on the other side of a lot of good cryptographers:
Filippo Valsorda doesn't work for Google. He left there several years ago. He runs an independent "buy contracts with me to support development of open source cryptography software" thing.
The person you linked to works for Google, which he seems to omit mentioning in the mail you linked to.