The article was referring to the USA situation. The difference between their situation and the Romans is that some of the people who played a part to the present situation (policies, laws, housing, blocking access to education...) are very much alive.

> Not many people in industrial Wales seemed to share in the benefits of colonialism.

I guess Welsh economy also profited (to a lesser extant) from slavery [1][2]. But if Normans purposefully enact systems that benefits them at the expanse of Welsh, solely (or even in part) because of their welshness, then of course you are legitimate to fight against it (if I understood you correctly).

[1] https://history.research.southwales.ac.uk/news/atlantic-slav...

[2] https://history.research.southwales.ac.uk/news/wales-and-atl...