There are a lot of people out there who are afraid of even a whiff of martial intent regarding tai chi. They may even have issues with competition in sporting events.
No doubt most among you have had to find creative ways to keep those students on board by describing the necessary interplay between health, relaxation, structure and martial intent. What works for me (currently) is this: when performing a move, I try to imagine a
duifang or counterpart who receives the move or martial intent. This counterpart is not acting as the recipient of violence, hatred or injury, but actually
completes the move or posture. For example, if I imagine the counterpart's arm in my hands, I place them correctly. And so on.
Now, to get over the idea of aggressive action, the student could imagine a friendly "oh, good hit old chap!" kind of contest, where both players have respect for each other, then retire to the bar afterwards and have a great old time. Or whatever.
Regarding the "this is not Karate" shouter, in hindsight, it would have been interesting to ask him/her in a calm manner, "why are you so angry?"
But what would have been the point ...? Hm.