I read it as "Yep and Amazon are not the only large company that use them, so watch out! If Facebook employees ever want to unionize, Pinkertons might/will be sent after them too".
Up/down vote I think is too ambiguous: there ought to be an agree/disagree metric and a relevant-interesting/irrelevant-uninteresting one too. Maybe even get rid of displayed karma and simply vote on multiple properties (insightful, agreed, brave, well-reasoned, informative, primary source anecdote)
Because "this is common practice" is often used as an argument that "this is reasonable."
Interestingly: McDonald's has their own internal surveillance apparatus that functions much like their own Pinkerton's.
> I wonder why multiple people read his comment as pro Pinkertons
It was stated as a whataboutism, which is a defensive tactic.
If the point was to indicate that the Pinkertons are not unusual, then that would be the subject. Instead, it reads as "this is not unusual", which is incorrect, regardless of intent.