One of the most terrifying parts of 1984 (the Orwell novel, not the year) for me was the memory hole - a physical hole in every office where paper containing illegal ideas or "wrong" information was dumped to be immediately incinerated. So much of what we know about the past and who we are today comes from the written record and interpretations thereof - it was basically erasing history as it happened.
For a long time, we didn't really have to worry about this sort of thing, because the physical infrastructure required for such a system didn't exist, would be prohibitively expensive to create, and would likely lead to massive protests if someone tried to create it.
But now we are in the digital age, and we have slowly been creating our own memory hole infrastructure, bit by bit, in the form of centralized cloud services. This deletion is an example.
Now, these service providers should be (have to be) allowed to remove whatever they want from their platform, but the fact that they can do so should be front and center in everyone's mind when they post content to them, be it code or text or video. We should be patronizing alternatives to github, youtube, facebook, and all other large centralized data stores as much as possible.