I don't think they normally pick model-citizen, salt-of-the-earth, kind-to-his-muvva, sit-in-the-pub-for-a-pint-and-a-chat types for Chief Whip.
Psycho bastard rottweiller seems par for the course for the enforcers of the MPs...so looks like they hit a peach in this case.
To be fair, he lost his rag with some coppers who were being jobsworths (they'd let him through the same gate several times previously that day); he'd probably had a couple with lunch, and he served up a volley of unappealing petulant abuse.
A bollocking, genuine humility, and some time spent seeing what a copper's life is really like getting puked on in a stab vest should sort him out. Put turning into a nice guy is not a realistic objective for an parliamentary whip.