I don't think "factually incorrect" is warranted. It's factually correct that the language is called Go. And while "golang" is a useful alternative for searchability and where "go" is taken, it is still a valid criticism to request using "Go" in natural language and prose. As for "official disambiguation", I'd say the most official thing said on the topic is this FAQ entry, which is quite clear on the matter: https://tip.golang.org/doc/faq#go_or_golang
(not saying Brad's comment isn't abrasive or rude. But it's not "factually incorrect")