If some guy sitting next to you on the train reached over and grabbed onto your junk, and then just stared at you with a smile...do you think you would be in th

If some guy sitting next to you on the train reached over and grabbed onto your junk, and then just stared at you with a smile...do you think you would be in the wrong to punch them instead of asking them to let go? Once you move to physical assault, you lose the defense of "you should have just asked me not to do that!"