Some people in opposition of removing controversial statues feel it is an attempt at erasing history. Statues can be seen to teach us about the attitudes and standards of the past, which may have been acceptable then, but are by no means acceptable now. They argue it is wrong to judge people from the past by today's standards.
While figures like Edward Colston are linked to acts that are undeniably evil by modern standards, history is complex, and no one is inherently or exclusively evil. Colston's philanthropic nature and generous charitable donations greatly benefited his home town of Bristol.
This suggests that there is a valid argument for controversial statues to remain.