What do you mean by "specifically targeting an individual front-end engineer at FB?" This seems to be "targeting" the person in control of the website of that open source project, and why wouldn't this communication be targeted at that person? Targeting it at anyone else, or just tweeting into the wind, would be completely ridiculous.

It also doesn't strike me as "harassment" or an "attack" or even particularly hostile. There's no threat, name-calling, or insults. What part of this is looks like harassment or hostility?