The issue with the protestors, is their tendency only to view history from their own perspective - in other words, take one aspect of Colston's life, and act on that.
History is far more complex than that, and part of the reason why history is so important is that it has got us to where we are now, and accepting it is a large part of making us a civilised society.
It is a not-lost irony that the very freedoms that Churchill fought for, allow people the 'freedom' to abuse his memorial now.
History evolves, attitudes to it change, but there is never an acceptable reason for mob destruction of anything, because the clue is in the term - destruction by a mob.
There is little doubt that due process would have seen Colston's statue removed in the near future, such was the discomfort at its presence, and that would have been the correct way for it to be removed.
It is neither valid nor rational to simply look at one aspect of history, and visit terminal vandalism on it as a response.