I used to have that problem with Designer whey as well. Since 100% whey, I could take upwards of 50 gram servings without an incident.
Oh, and the myth wasn't saying
only on an empty stomach, I think you misunderstood. It's saying anytime. On their train of thought, if you ate 2 cans of tuna or a 10 oz steak, would you get the shits as well?