As for abusing, I have seen Parelli (as well as every other NH trainer out there) disciplining a horse. Discipline as well as whips, spurs, bits, etc. are not abusive, the abusive use of those is.
But there are some who believe that ANY use of said items, apparently especially
bits, is abusive, and anyone who uses these tools are ignorant Neanderthals who care nothing about horses or their well being.
These same persons also appear to have no real conception or understanding of other types of training, and that training must
be abusive, because again, it uses those horrible torture devices known as bits.
There are many roads to Rome. On that MOST of us can agree, except for a few who are blinded by only one particular type of training, and dismiss all others as ignorant and unenlightened.
I know of no trainer, except for that crazy Russian of Haute Ecole infamy, who doesn't
use disciplinary tools as well as regular tack, including bits. Riding bridleless and tackless is fine for exhibitions or photo ops, but when it comes to actual disciplines or horses who have real jobs those things aren't just required, they're necessary
. That holds true whether you're a fan of Parelli, Zettl, or Morris.