Of course the ball carrier occupies a special position. But that doesn't mean he has to take steps to prevent the tacklers from committing illegal actions. It's the tackler's respsonsibility to avoid doing things that are illegal. Saying the runner "had time to protect himself" because the tackler has grasped the collar but runs with him before pulling would be like saying the runner should have protected himself when a tackler grasps the face mask and then runs with him a while before he yanks on that mask. My question remains, is the intent of the "immediate" part of the rule to be from when the grasp is made or from when the pull is made? All the videos I remember were presented with the grasp and pull being almost simultaneous, it's the delay in bringing him down after the grasp and pull that seemed to negate the foul.
I agree there are plenty of legal hits the runner can take that are potentially far more dangerous to the runner than a HCT. Shoulder to the head of the ball carrier being illegal? Maybe if I deem him to be in a defenseless possition. Does it seem odd to me a shoulder to head hit is ok but a head to head hit is not? Yes. I'll bet we will soon be in a situation where any head shot anywhere will be illegal, but that's probably a different discussion.
I don't think I "compared" the HCT to an US call. What I did state was I found it odd that some officials are quite willing to find an excuse not to call contact safety fouls but are more than willing to call the US foul with the slightest provocation. That's not comparing fouls, that's questioning official decision making.