At its best, psychoanalysis is the classic therapeutic technique for exploring unconscious processes. At its less-than-best, it is a jargon-opacified, oedipus-complicated, libido-theoretical, pseudo-scientific cult whose messiah is Sigmund Freud.
Source: wiktionary
They haven't, largely, because the debate has been deliberately opacified, with nationalist and Conservative politicians in particular still seeking to portray British Imperialism as a source of pride and Britain as the "good guy" in the slavery debate.
Source: wiktionary