My opinion, do the assignment. Imo it's not offensive because you're trying to understand what being a stutterer feels like on any kind of a first hand basis. I don't care how naturally empathetic someone is, if my slp can't even try to put themselves in our shoes with a mock stutter, I don't want to hear from them. Go stutter with someone over the phone, then go stutter with someone in person. Go hold 5 second blocks in line at Starbucks, or asking a stranger for directions, or anything.