Asian nations have done drastically 
   worse to each other

Coincidentally, this is true of Africa as well: Mengistu Haile Mariam, Mobuto Sese Seko, Idi Amin, Samuel Doe, or the Tutsi/Hutu conflict were typically much more violent than almost all colonialist behaviour. (Naturally the natives have been colonialising and enslaving each other too.) It's good never to forget this.

That does not mean that colonialism was great, or that anybody wants it back. Hopefully humanity has evolved towards better ways of dealing with each other.