No one gesture or action can fix race relations. Just as racism is a societal problem that manifests itself in many ways from tiny things all the way up to awful explicit actions, societal change needs to happen in both large and small ways. Things like having an 'end racism' banner by itself doesn't do much, but it's part of a collective effort to show that society is changing and to remind people that we need to and are doing the work to tackle the issue.

The only thing racism needs to thrive in society is for it to be quietly tolerated. Removing this banner can be seen as a backslide in that direction.