Common meaning:

Taking items out of a knapsack. 

Hidden meaning of the Equity religion: 

The privilege white people have over non-whites because they are able to see themselves represented in society.

Discussion: 

Equity says that one of the privileges white people have is when they look at movies and advertisements they can see themselves represented in society. These white people need to examine this privilege, or as the Equityists would say it, unpack their knapsack.

One of the main points that has been emphasized by Equity leaders is that white people, and particularly white males, have had so many examples of themselves in culture that they received an advantage. This may have been somewhat true thirty years ago, but it is no longer the case.

Since the Equity believers have a particular hatred toward white males, they have been doing what they can to eliminate them. As they have taken over control in various media companies, they began to remove white males from advertisements and movies. Most of the white males that are left are portrayed as weak and stupid.

The contents of the knapsack have disappeared, but the Equity believers don’t care.