Not a “grip” nowhere is the action described as a grip. To forcefully grab hold of another person’s private parts is assault. You and everyone has the right to determine the boundaries of physical contact with another person. When those boundaries are aggressively breached (so to say) the law is clear. It is wrong. When the aggression is sexual there are all kinds of descriptions in statute to describe the different degrees of assault.
Also nobody gets to decide what events are traumatic to another. We don’t know the personal history of this man and what factors made this event traumatic for him. I think determining a valid diagnosis of PTSD is best left to professionals. Is the term PTSD sometimes used to describe non medically diagnosed stress? Of course it is. And that should be made clear.
By the way thanks to your stepfather for his service.
I'm going to go ahead and keep the opinion that this is a melodramatic preliminary to a financial shakedown, but you think what you want.