I may have missed finer details watching on my phone but on first watch, i don't believe Sam and Whitehead can be compared.
Sam went in with intent to hurt the halfback and made contact with the head. Two weeks is a very fortunate result as it could've been more, especially if he had to be taken from the field.
Whitehead, while cheap, was correctly penalised twice but never touched a head from what i saw.
You simply can't make contact with an opponents head in sport and if you go in with the intent to hit and make clean contact then it needs to be treated as intentional, regardless of whether it was or not.