He's looking at it wrong. He needs to realize that Jon lost the fight before he entered the cage. He cheated by taking illegal substances. Had the test results come out prior to their fight, the fight would never have happened and DC would have went on to face the next contender. Jon once again took himself out of competition, leaving DC as the rightful champion.
Let's say Jon and DC were playing Checkers and DC was already up 3-0 games on Jon. On the 4th game, DC gets up to go take a leak, and Jon screws with the board to gain an advantage while DC is away. Then DC comes back and Jon wins the game BUT there's a hidden camera in the room that shows Jon clearly cheated. DC is not now 3-1 against Jon. He's still 3-0 and hasn't yet lost to Jon, because Jon cheated and made that game void. He's not "better" than DC and DC should have zero reason to feel bad that he "lost" to Jon. Stupid analogy, I know, but that's how I see it.