The comparison of what Paras did during Apache and what US units did is rather stupid. It's not like Afghans were attacking US civilians on US soil. On the other hand, Paras beheaded the Pakistanis to send the message across that your brutality will be paid back in kind.
Most of such gnarly executions and theatrical brutality that our SOFs do has had a purpose, the purpose being the dissuasion of attack on innocents (and revenge for mutilated troopers).
On the other hand, what US did was invade Afghan/Iraqi homeland, killed their people and start having competitions on the number of kills they could manage, start using their unit specific symbolic weapons like hatchets to mutilate bodies and overall being a steaming pile of shit human beings.
There's a difference between purposeful carnage for causes close to the heart when left with no other option and psychosis induced brutality for the sake of being brutal.
How well did USA's troops mutilating dead bodies serve their hearts and minds mission in Afghanistan?
It was a counterproductive move, was it not?
On the other hand, our troops weren't trying to win any hearts in Pakistan. What they did was dissuade the Pakistanis. Purposeful violence and messaging.
Psyops =/= Sadism.