Not only is it highly unrealistic that language would mutate that severely within 40 years - yes, it's undergone some shifts between 1969 and now, but nothing like the drastic differences portrayed here - but it's also just plain DULL.
For a guy who's usually so up-front about owning his source material, I actually would have respected Moore MORE here if he'd simply had one of the hoodlums refer to his friends as "droogs," so that he could be HONEST about the fact that he's flat-out aping Anthony Burgess' wordplay here.