The trouble with this, of course, is that you build an echo chamber for both yourself and your friend. You no longer see the posts you think are BS, and you preclude yourself from challenging your friend's BS in comments.

I agree that delegating to Facebook judgement of what speech is acceptable or not isn't a good idea, but the flip side of that is you have to take a slightly more active role in cultural discourse if you have any desire to see society converge on good ideas, and eschew harmful ones.