Bearded Viking Admin...
Join Date: Oct 2002
Location: Ossum, Texas
Motorcycle: '08 KTM SuperDuke R, '99 SV650S, '84 XL600R
Re: softer fron tyre than back
Lots of racers use a softer front, including myself. The main reason is that when you are pushing the grip limits, a hard(er) rear is more likely to slide before a soft(er) front and a rear slide is WAY easier to control than a front slide.
Also, the rear tire takes more "punishment" so being harder it'll last longer.
If you watch MotoGP, they usually show the tire choice of the front runners at the beginning - most often they'll have a softer front too.