Sounds to me like this Colston was a significant figure in Bristolian history, so I think his statue should go back where it was.
We should not be eradicating our past due to the fact historical figures did not share the views upheld in the current day. I doubt, for example, that Alfred the Great would have been pro immigration, or that Wellington was a lovely fellow. But these are the people who helped create the world we live in today.
Similarly this Colston seems to have done a lot for his city, so to try and sweep him under the carpet, while doubtlessly enjoying some of the stuff he left behind, seems wrong. You can always put him in context by teaching about him:
Colston's name permeates the city on buildings and landmarks. Colston supported and endowed schools, almshouses, hospitals and churches in Bristol, London and elsewhere. Colston constituted his charities to deny their benefits to those who did not share his religious and political views.[1] Many of his charitable foundations survive to this day.[5] In Bristol, he founded almshouses in King Street and Colstons Almshouses on St Michael's Hill, endowed Queen Elizabeth's Hospital school, and helped found Colston's Hospital, a boarding school which opened in 1710 leaving an endowment to be managed by the Society of Merchant Venturers for its upkeep. He gave money to schools in Temple (one of which went on to become St Mary Redcliffe and Temple School) and other parts of Bristol, and to several churches and the cathedral. David Hughson, writing in 1808, described Colston as "the great benefactor of the city of Bristol, who, in his lifetime, expended more than 70,000L. [£] in charitable institutions".