I have not been following the Sad Puppies controversy in detail, so my comments are very general. (And am so not touching Gamergate, which deals with a particularly intense subculture I have only passing acquaintance with.) However, the Hugo Awards controversy reprises similar controversies in other fields; hence the general comments.
(1) Be suspicious of arguments from quality.
Quality in artistic and literary endeavour is far from an empty concept, but it is also far from an entirely objective one. Which leads it open to all sorts of contention and hi-jacking. In particular, it is absolutely standard for supporters of the status quo to make the argument from quality--i.e. we don't have any black/female/conservative/... writers/announcers/artists/... not because we are prejudiced against them, but because there simply aren't any that are good enough.
(2) Diversity has varied dimensions.
Racial and ethnic diversity is one sort of diversity. So is diversity in ideas. They have no necessary correlation. People of varied racial and ethnic backgrounds are likely to have varied experiences but that does not, of itself, lead to diverse ideas.
(3) Covert politicisation is easy to not see and hard to fight without engaging in overt politicisation.
All the various groups marching down the Emancipation Sequence have engaged in overt politicisation and been condemned by supporters of the status quo for doing so.
(4) Critics of Sad Puppies are using fairly standard Defenders of the Status Quo arguments.
Arguments such as: nothing to see here, those over there just troublemakers subverting standards of quality, they are politicising what as working just fine ... . Which, of course, makes said critics the Embattled Establishment. Not the self conception the Virtuous like to have, but that does not make it any less true.
quick Google suggests that mainstream media coverage has been largely fairly awful--engaged in identifying who are the Bad Guys and holding the status quo to be unproblematic (which, by definition, means that no critique thereof has any legitimate basis). But that is also a recurring pattern when the media is largely on the side of the status quo.
Would it be better if the Hugo Awards had not become subject to overt politicisation? Probably: but folk should have thought of that before they began judging writers by their personal beliefs (or rumours thereof). But that is the problem with Virtue signalling: it is subject to Virtue inflation--both in ever finer moral distinctions (such as making a big moral deal over the difference between "coloured people" and "people of colour") and ever broader range of social matters to signal Virtue over. To be ever more socially invasive is it basic logic.
Particularly as part of Virtue signalling is to hold that the said Virtuous have a monopoly of moral legitimacy, so it is just fine to exclude folk of different views from social goods. But other folk may care about their, for example, SF too, and are likely to respond.
For a useful corrective, recovering a sense of nuance and moral diversity, I recommend this essay by Jonathan Chait on the dynamics of US culture war debates. Or, in other words; people have differing views: get over it and lets get back to SF as fun.
ADDENDA: George R R Martin on the controversy. Larry Correia, founder of Sad Puppies, replies.