Are we as consumers okay at the professional RPG industry refusing to do business with someone over a mere allegation? Because I can see this quickly leading to some innocent people hurt sooner or later.
The idea that this backlash exists the result of a "mere allegation" downplays the scope and nature of these allegations (plural). In particular, it's that 1) these allegations are about an individual with well-known toxic behavior (and lots of red flags), 2) these allegations came from his ex-wife (among other women) - whom the individual in question used as a puppet account for shielding his own toxic behavior online - and 3) the serious nature of these allegations rooted in sexual assault, rape, and abuse.
I also think that this immorally misplaces the moral obligation here. This is not about protecting hypothetical innocents that this may hurt, but, rather, about believing the actual victims of abuse who have been hurt by this individual. Worrying about hypothetical innocents of false accusations is attempting to deflect, derail, and damage the allegations made by abuse victims when they do arise through shifting the moral question to protecting a hypothetical class of corner cases. It basically hides the actual abuse committed by abusers behind the shield of hypothetical innocents, who constitute a slim minority of cases.
The below is a lot to unpack.
If they are acting on more than the allegation, and are in fact reacting to known behaviour of Zak S or so strongly suspected behaviour that they feel confident in their current reaction: What the heck was the RPG industry doing up until now? If Zak S is so bad that he should have every mention of him removed from the RPG industry, why didn't they do something before now?
Hence a lot of the current outrage. The tip of the iceberg toxic behaviors were publicly known and reported during the time of the D&D Next playtest and were left to fester in the community until now. (And a big part of the anger and disappointment is not just about Zak S but also on how Mike Mearls enabled and facilitated Zak S's toxic behavior.) This is not just about what Mandy Morbid reported Zak S did, but also about how the Industry turned a blind eye (or actively defended him) to a prominent toxic person who committed harm against the TTRPG community.
Also a critical difference from the time before these latest allegations is, again, the nature of the allegations, namely rape and sexual assault, as well as the current #MeToo movement, which really only began in the Autumn of 2017. The #MeToo movement has helped bolster and create a platform for victims of abuse in public spaces.
I certainly wasn't surprised to see the most recent allegation. So why the heck are they pretending to be surprised? And if they didn't have any suspicions, why are they taking such drastic action against someone without any legal proceedings occurring?
Some people should have known better, and there is no excuse for their surprise. For some people though it was a surprise, and they may have had their legitimate reasons for being surprised. Ignorance is bliss for some. Some people are not plugged into the social scene behind the publishing or the person's community engagement. If you only bought one of his books at a game shop because the staff or friend recommended it, you would likely not be aware of the author's full reputation. They either do not even know who Zak S is or his reputation in the community. Some people likely had suspicions but overlooked them because they believe the best in people (particularly those who may have regarded him as a friend), or they never personally experienced the problems themselves, or they were fooled by Zak S. A blog post by Mandy Morbid had provided Zak S with his most commonly cited shield against criticism. Even Mearls pointed to this blog post when he gaslighted (and dead names) victims of Zak's abuse and harassment. But we only fairly recently had it confirmed from Mandy Morbid that it was not her who wrote it. That revelation left a LOT of his defenders and apologists with egg on their face.