I'm not fully opposed. People mention that walking backwards is pretty easy... maybe on a track. In sand, on grass with rocks and tree roots, on an uneven stone path, it gets more difficult. Tripping is not fun.
You just look backwards and it's as easy as walking forwards.
well then turn your body and run foward, away from the knife. moving backwards represents the real life movement backwards, and when we move backwards, we move carefully to not fall (since falling is not possible to do ingame).
in an unrelated note, i would like knife (and melee weapons in general) to be able to fire when running, since ....well you know, you are charging ! you run fast and stick the blade at full speed to do mayor damage