You don’t even have to unfriend them. Click the top right button, the one with a sort of “v” sign; then, where it says “Subscribed to —”, choose “Only Important”. That’s it. You will be seeing nearly zero posts from them, and can revert at any time.
But, come on, do you really need that kind of friends? Something to think about. Hard to say, I don’t know them :P
I dumped one awhile back...
I thought about it for a nano-second and *poof*...she was gone! It felt GREAT not having to look at that (old) picture of “poor” young Trayvon, day in, day out.