We don't know his environment. We don't know his company's policies. We don't know his hardware, connectivity, or budget issues. These kinds of passive aggressive responses are almost never helpful.
That’s not a surprise, and maybe the issue at the core here is not really Docker. That’s all.
I've seen plenty of stuff in my career where I've gone on record to say "hey - we really shouldn't do this". Nothing got done about it. But hey, I did what I could.
Recently I learned about Rasmussen's dynamic safety model. I think this is a very handy mental model to have. It's the human factors that make what we do really hard. Often line level practitioners know better than they are allowed to do in practice and trying to fight organizational politics to Do The Right Thing can be an uphill battle.
Aside from anecdotes, there's little value in further discussion beyond the PSA that is the original post; save for prevention/recovery of such events.
They may have valid reasons to do that, even if not common.
export $WORKDIR=Home/me/proj
...
rm -rf /$WORKDIR
If something unsets $WORKDIR or does not set it at all, wave bu-bye to your everything. And before you say "who would do that?!" -- I believe I heard that happened to a build of RedHat that also had some kind of force push and auto-pull and build on their version control so every connected person had their version of the software nuked. If not for the non-connected individuals, the entire software would be gone apparently. Or so the legend goes.
2. Why are you running docker on ad-hoc machines you need to prune?
3. Why do you even need root access on production machines to fiddle around with docker commands?
While this is obviously a bad bug (and there are many with Docker), it seems more of an operational procedures failure than anything else. You could be saying:
“Beware of rm -rf /, it just deleted 20gb of production data”
Ok. Sure. But why are you tools and procedures putting yourself in a position to make that mistake?