They established two kind of colonies - one which exploited man power and natural resources, and the other was territorial and treated as a natural extension of their own kingdom (after they conquered and replaced the orginal habitants with their own citizens). All the Asian and African colonies fall into the former category where as all the "white mans land" - Australia, New Zealand, Canada, USA - falls into the latter category. (I know some Americans would debate that they were in the exploitive category too, but as an indian I'd disagree).
I don’t know where your argument is going, other than that hey they stopped doing this bad thing. My original comment was about how colonies got nothing in return from the colonizer. You chose to state a tangential point, that the slavers stopped slaving.
Some people in the British Empire took part in the slave trade, and those people should be condemned. Some other people didn't. They fought against it and when they were in power they stopped it and expended considerable resources stopping others from doing it. Those people are praiseworthy, even though they were part of the British Empire.
I’m saying Nazis+Hitler should be condemned, never mentioned Germany. Similarly, I said Great Britain, both the monarchy and their colonial companies and the government resulting, which is what the article talks about as well. Never mentioned the citizens that fought back shouldn’t be acknowledged.
Furthermore, they didn't "enslave colonies". They established colonies. They conquered nations and territories. And they shipped slaves, a minority of whom were captured by British slavers, but most of whom they bought from Arab and African slavers.