Nah, dude, you're wrong.No Guard STAB moves have normal accuracy against Protect/Detect.
So DynamicPunch has a 50% chance of hitting through Protect/Detect.
It would seem non-STAB moves are exempt from this though. Odd I know, but it's what it says in the research thread.
I've used No Guard Machamp before- Moves with 100% accuracy have a 50% chance of hitting through Protect/Detect with No Guard.
Used it against a Yanmega, he used Protect, I used Ice Punch, and it hit.
Probably, its some glitch with the weather.