My take, Sunny, is that they feel really guilty, but don't want to accept those feelings. So, they turn us into the bad guy, deserving of their anger, so that they can look themselves in the mirror. Or perhaps it's just that they are the kind of people who cannot look inward, so they need to find an outward source of their unhappiness. It must be us, right?
My H still seems so angry with me-- he's told me that I "make" him feel guilty, and resents me for that. (What on earth could he possibly have to feel guilty about?!? haha). What power he gives me over his feelings. I feel sorry for him.
Try to let it roll off- so much of this is just not about us AT ALL. The more I detach and live my life apart from him, I see that clearly.