No one is saying the trainer should be allowed to run in front of him. I think everyone can agree some kind of punishment or sanction is warranted and perhaps a rule change to prevent it going forward, IE retake the kick or move it in front.
All that being said, The trainer is not the reason Campbell missed, he is just another distraction in a stadium full of distractions. He shouldnt of ran in front, but if JC was distracted or put off he had every opportunity to resent and refocus and take the kick like every other kicker in the nrl would have done, At the end of the day he missed, Nath nailed a much harder one to tie it up and the rest is history,