I loved this article. I was glad not to fail your test. This "thug" one made me laugh, because I nearly always use the word in the phrase "police thugs".

The word "thug" does have its origins in the British occupation of India - it refers to the Thuggee religious group in India, which the British exterminated, because the Thuggees did actually practice ritual murder at least at some point, but it's also the case that the British overstated the threat considerably.

I personally think it's fine to use on cops, though. YMMV.