The fact that you Musclemania pro entered a competition that was advertised as natural, knowing full well that you had an unfair advantage over (probably) most of the competitors, and smiled after you were given the trophy (or stole it depending on your view point) makes most people here lack simpathy for you.
I think the justification is that every pro in Musclemania is not truley natural. Every amateur overall winner is not natural. So it's a level playing field, just not what the audience thinks it is.
Zwick doesn't make his money directly from the contests. These days there are hardly any contestants, and not many more people in the audience. The real money comes from TV. Not in the US of course, but Musclemania contests (including the model search) are very popular throughout Latin America. (From the TV schedule on the mm website, it seems to be popular in South Africa too.)
If Zwick had truley natural guys winning his contest, his ratings would plummet. In Latin America, the US, or Europe, we've all forgotten what natural looks like. Steroids mean looking like an IFBB pro. Put a real natural guy on stage, and they'll probably call it a swimmer's build.
Zwick is a TV producer. He's giving the audience what they want. Beefy guys who claim to be natural, but aren't.