This week, I was reading D&C 121:34-46. I thought some about how I "undertake to cover [my] sins, or to gratify [my] pride, [my] vain ambition, or to exercise control or dominion or compulsion upon the souls of the children of men, in any degree of unrighteousness." Since God knows everything, the idea of covering our sins from Him is nonsense, so this must necessarily be about covering our sins from others. I thought of D&C 58:43, how confessing sins is part of repentance. What's our motivation for secrecy regarding our sins? Pride. We don't want others to lose esteem for us when they know the things we've done.
It seems to me, then, that a stumbling block to confession is a judgmental mentality of others. I'll be more likely to confess to people who will maintain their esteem for me, and less likely to confess to people who will not. So part of becoming a more-perfect group involves allowing for the complete repentance of others by learning to be less judgmental.