Never heard that thug just refers to only black people. I don’t live in the US, so maybe just there. I looked it up in several dictionaries and did not find one that defines it as black people only. I can find lots of literary references where it is explicitly used to refer to a white person/people who is/are thug(s).
If you feel you have the authority to call people racists for using the term thug, can you please provide some supporting evidence of your definition? And also provide us with the politically correct synonym of thug that is not race-specific. If we eliminate thug we need to replace it with a term that holds the original meaning.
Edit: OK, I found this. https://www.npr.org/2015/04/30/403362626/the-racially-charged-meaning-behind-the-word-thug
The term originated in India and was adopted by the British. Rappers used the term to refer to themselves. Now white people can’t use the terms anymore (even to refer to rappers), but black people can use it. In this way, it is like the N-word.
So, white people, stop using thug. Only black people can use it. Instead, white people should use “ruffian”. As far as I can tell this only applies to Americans. For the rest of the world, thug still means thug.