It is not all the sudden as far as I can tell. There's a long history of Go hate, and it makes sense to me. Go is a new(ish) and fairly popular language, which already guarantees some level of hate. More substantially, it is an implicit argument against most things language enthusiasts like about programming languages; it's lack of static features and dynamic capability, it's non-focus on optimality in any domain, there's no attempt at uniform elegance or a motivating theory, it's just a kinda mundane procedural language that tries to solve some problems C enthusiasts had while avoiding the things that bugged them about Java and C++ (to oversimplify). A language such as that succeeding socially and practically is borderline offensive to folks who love clever language and runtime design, who love things that can push the boundaries of performance or verifiability.

Something so apparently mundane and poorly thought getting traction is a regression in the world of software engineering, supported by a Big Evil Corp that many folks dislike.

I've also personally seen a social meta-effect of this, where in a particular space all of the language aficionados would make a point of dumping on Go whenever Go was discussed (or even when a dig at Go could be shoe-horned into another discussion), and at a certain point there are only negative discussions of it, and the snobbery (justified or not) is a form of social bonding.

Of course, there are loads of legitimate criticism to be applied to the language design, the runtime, the rollout, the marketing, the framings of the authors, but there's a persistence, a snarl, to some of the critics that seems to me to go beyond an observation of the real issues. For reasons listed above, some people seem to take hating Go quite personally.