For me, leg energy is for forward movement. I'm happy to let a brake do the work to slow me down. Thus, using leg energy to slow down it is pointless. I commute 150 miles a week on my fixed gear and race my gearie on the weekends. If I spend a lot of time backpedaling then that puts me on the Metro for a day to rest, or leaves me flat-footed in a race. That is pointless to me.
That said, it is a free country, do what makes you happy; I'm just sharing my viewpoint. Got a brake, go ahead and use it. The style police won't come and arrest you. If you'd rather back pedal, no one says that is against the law either. Live and let live. I'm just saying that it is stupid to have a brake and feel guilty about using it.