I do think it was a pen (stupid by the defender) but I also think there was over-simulation (to say the least) and that is annoying. The solution to this is to introduce rules that allow a booking for over-simulation (drop the word diving as that suggests there was no foul) and still reserve the right to give a pen. By the separating the two actions (and there are two actions in place here - one by the forward and one by the defender) it will remove pressure from the ref and allow a more balanced ruling on the decision.