People are fickle regarding things they are fans of - all the more reason that's it's a bad idea to be famous.
Rebecca Mayes was (and maybe still is) a very good video game critic - she's not as good of an artist as Yahtzee but maybe as good of a critic. Her material was fairly centrist and definitely not "SJW extremist" in any sense - it was far more centrist than Anita Sarkeesian's work, for example.
The impression I got from the ordeal was that Mayes was concerned with Yahtzee's disgust for humanity, perhaps especially since Yahtzee himself is human. Possibly the "right" approach would have simply been to research misanthropy, think seriously about it, and then make either a public or a private criticism to Yahtzee of why misanthropy is psychologically and socially unhealthy and that he could consider getting rid of it within his personality. Possibly because of her attraction to him she didn't take the "right" approach, but what she did was reasonable enough considering the circumstances.
The internet being lethal and unforgiving did what it did, and the rest is history. The lesson we all learned was that Yahtzee's misanthropy is part of his artistic and critical construction, thus part of both his fame and his livelihood, and that's more important to him than not just his psychological and social health, but the happiness of the people who care about him.
Don't get between a man and his demons, especially when those demons pay the bills.