Your own definition debunks you. 'especially when considered with reference to social and cultural differences rather than biological ones,'. Also, I'm not denying that gender and sex are used interchangeably by some people, especially in the past. Where did you get this definition, perchance?
I raise the question again, by your logic, you are justifying colonisation. Taken to its logical conclusion, you wouldn't complain if Arabs turned up in ships and stole Europe's wealth by resource extraction?
I've explained numerous times in the comments here that biological sex does not equal gender, that is a FACT that you cannot disprove, so I'll leave it there.
