That one I agree with.
At least somewhat seriously.
My opinion of all these people who are declared to be bad men because they were racists is that we cannot judge people based on standards of today. If they did great things, and they were racists, I'm not going to say that they were bad people if the entire culture in which they lived consisted of bad people. I can honor them for what they did, if they did something worthy of honor, even if not everything they did was worthy of honor.
I had to look up Edward Colston, and everything I know about the man is from one Wikipedia article, but it seems to me that he started a bunch of charities, and some of the charities he founded still existed at the time the statue was erected, and still exist today. That's worthy of praise. That remains true even if the source of the funds was a profession which today we find reprehensible. Reprehensible or not as we see it today, at the time it was a perfectly respectable profession, and had he stopped doing it, the same money for the same "goods" would have gone to people who would not have founded a hospital with it. He did good, even in the midst of a society that was rotten to the core, and even if he shared some of the rot.
As for Leopold of Belgium, I don't know too much about the man, but from my understaning, pretty much all he did was to grab a colony for Belgium, and to do so with incredible cruelty and bloodshed. In other words, I don't know of any great thing he did. The only thing he is remembered for was something that today we would find to be evil. So, very well, take down the statue.
So, if someone is honored for doing something evil, even if he did it very well, and the people of his day did not consider it evil, then take down the statues. If, on the other hand, someone did something that we consider great, but they lived in a time where evil was considered acceptable, and they participated in the evil, leave it up.
Churchill, Lincoln, Washington, apparently some fellow named Colston are not being honored for being racists or being slave owners or slave traders, even though they may have been those things. They are, and ought to be, honored for the good that they did.
In the case of Leopold II of Belgium, I'm not aware of anything worthy of honor. Maybe there was something and I'm just not aware of it.