Tl;dr - if Labour want to combat racism, they should say racism is wrong, over and over, and act on that belief (e.g. by leaving certain social media sites owned by racists). That would do more to promote anti-racist norms, and protect the interests of Britain's minorities than immigration controls.

There is abundant evidence in the social science literature that (a) social norms matter (b) political elites play an important role in setting and reinforcing social norms (c) that 'unexpected' rhetoric behaviour (e.g. centre left sounding intolerant) has more powerful corrosive effect on norms.