Comment by seabass

Dorsey has explicitly stated that because user-defined filters will lead people to remain blissfully unaware of ideas that challenge their own, he does not want Twitter to follow that path.

It's a tough call. In some sense, for any global website that doesn't want to impose its own moral code upon the world, it makes the most sense to be hands-off and let users judge for themselves what to see and what not to. On the other hand, doing so would amplify the echochamber effect that's already strongly present on Twitter.