I was a direct witness of such a brain washing case a few years ago. Google was about to release a new version of Android or of Nexus phones. (I don't remember the exact details) And there was an insider leak, so the details of the innovation were published on internet a few days before the official announcement. Leaks are now very common and often organized by companies, but a few years ago it was not yet the case.…
There's a lot of work that goes into those announcements. It's not just advertising the product that is the goal, it's presenting it their way.
Similarly, when someone is telling a joke and someone else tells the punchline, they get upset about it. According to your logic, they shouldn't. The joke was told, and the audience heard it. But I've yet to meet anyone who wouldn't be upset about someone else telling the punchline to their joke.
They were not brainwashed. You were incredibly insensitive to their feelings.