I also have a friend named Sammy, who's a doctor. Last night I discovered Sammy got a new job at Planned Parenthood, where a significant part of her time will be spent performing surgical abortions.
How many articles on the web should I read before I'm allowed to stop being friends with Sammy?
Also, do you have the same feeling for the reverse situation? If instead of being an employee, you're the boss. You're aware that your employees are doing something morally wrong and you do nothing to stop them, but you aren't doing it yourself. Do you have any responsibility? In the ethics of war, there is the concept of command responsibility[0], where leaders are responsible for the actions of people under their command. Do you think that is a bad doctrine because the leaders aren't the ones shooting people? No one dies through their individual actions even if their subordinates commit war crimes.
Have some decency to call your actions what they are.
If you want to harm somebody in retaliation for doing something you don't approve of, don't call it 'the opposite of harassment'.
This pretty much looks like harassment to me:
"the developer community need to start ostracising people working for these companies. Don't hire former employees, don't hang hang out with people who work for these companies and conferences. Don't supply services to these companies (build their website, network...)."