Fighting-back can be very dangerous when working with Sifu.
If Sifu is teaching you something, and you are deliberately awkward or try to catch him out - then things may become somewhat unpredictable.
Instead of showing what he is intending to show, Sifu will adapt, change and improvise.
One way or another he will illustrate the lesson he has planned.
The worst case scenario with resisting is that you may break your own arm or otherwise injure yourself.
Luckily, we've never had a breakage in class, but we've had plenty of students who bite off way, way more than they can chew. Myself included!