Not to defend "Capitalism" (or this specific instance of downsizing) but do they think there would not be some sort of workforce allocation mechanism ("layoffs"), and one without any friction, in a different system ? There's plenty that could be done to mitigate the effects or to remove the incentive for companies to part with workers at the drop of an hat.
They're consolidating their back offices, because there's no real reason for Blizzard and King to have their own PR, social media and customer support departments in addition to Activision's own. Additionally, with Heroes of the Storm shut down and Destiny returned to Bungie, a bunch of jobs in the same areas no longer exist. So this specific instance seems perfectly valid and would have happened regardless of their 2018 earnings. I'm certainly not a fan of Activision, but streamlining their operations and using the money to hire more actual development staff, which is what they plan to do, seems totally sane and understandable. The only issue I have is that this step was a long time coming, yet the layed off workers didn't get advance notice. That's just shitty and wouldn't be legal in any EU country as far as I'm aware.