Why are they stripping Reggie Bush's Heisman Trophy?

I think its kinda of messed up because you cant just take something someone already won. Its like taking away superbowl championship from a team, or taking one of michael jordans MVP trophys away from him. he earned that trophy with his blood, sweat, and tears. how can they take it away from? im not even a reggie bush fan but still think thats messed up.