pick the scab 

to ditch an unwanted group member

to express the desire to be rid of a member of a group.

yo, jon's fuckin' annoying. Let's pick the scab.

pick the scab by Deeeee November 1, 2006

to pick at the scab 

picking at the past, memories of that unwanted experience, and at any undesirable present condition:

"What is unique about Helms - and from my viewpoint, unforgivable - is his willingness to pick at the scab of the great wound of American history, the legacy of slavery and segregation, and to inflame racial resentment against African

to pick at the scab by rabuanm June 11, 2012