Some tweets and a Sam Biddle provocation piece about Google keeping this person employed (from 2 years ago) != a blacklist. Even if this amounted to action on Google's part, an employer has the right to fire an employee for actions deemed hostile to other employees (and its plausible to say its hostile for an employee to write blog posts about how certain races are genetically inferior). This is implicit in the concept of "at-will employment". I've been on the receiving end of this taken to a ridiculous extent when I was fired from a job for not going to a Christmas party. I found the reason I was fired to be pretty objectionable, but it wasn't anything remotely like being blacklisted.

There's a lot of hypothetical rabbit holes to go down with this, but ultimately this is a distraction from what's being discussed, which is a person choosing to withdraw their workshop group from a conference because of the opinions of a speaker. Boycotting, protests, or simply declining to not participate are fundamental methods of democratic action. It's laughable to me that anyone would equate what's being talked about here with a suppressive measure.