He's absolutely right, though. Who would you point to in the UFC and say 'that guys is clean'? Maybe Mark Hunt or Daniel Cormier? But DC put is hands on the towel during a weigh-in. He knew he couldn't make weight and rested his hands, taking 2-3 pounds off the scale. That's cheating right there. It may not be PED level cheating, but it's cheating.
He's not saying every top athlete is using anabolic steroids and cheating the max. He's just saying that they'll find some small way to cheat and get an edge. Many athletes boost their hematocrit by drawing blood from themselves and storing it, then injecting it later before the fight. You can get more red blood cells this way and thus slightly better cardio. If done right this can be difficult to detect and confirm blood doping. This may not be outright EPO doping to boost red blood cell production, but it's pretty darn close.
As the saying goes, "if you ain't cheating, you ain't tryin".