Why should we be so keen on ‘inclusion’?

One of the most popular buzzwords in modern Britain is ‘inclusion’. It dovetails neatly with, and is often used alongside, the word ‘diversity’. Who is it that we wish to include though and why is exclusion seen as an evil?
Popovic, Celia Frances (2007) Why do Medical Students Fail? A Study of 1st Year Medical Students and the Educational Context, Birmingham: School of Education, The University of Birmingham.

should‘inclusion’?