For a start, sexually-abusive language is part of their speech. They might be able to see that calling a black man a nigger is racial abuse, but they cannot see that using the so-called four-letter words is sexual abuse. For them that vile form of speech is so normal that they have rendered themselves incapable of hearing what it really is. The Roast-Busters are only expressing physically what most people are constantly expressing verbally.
Even when their language is not drenched in four-letter words they speak and act in ways that manifest an abusive attitude to the human body, in particular to the parts that are the emblems and the very essence of manhood and boyhood, girlhood and womanhood. They mock them, they belittle them, they denigrate them, they regard them as a filthy joke, they think of them as filthy and treat them as filthy, they use the vile words that mean them to hurl abuse at anything they loathe. Then they wonder why people treat men and women badly. They do it in speech all the time, so they should not be surprised when so many do it in practice, and that a few openly boast about it on Facebook. That same boasting is part of their speech and their thinking.
Worse, many, perhaps most nowadays, are not bothered by, indeed practise as a 'normal' part of their daily lives casual sex, flitting from bed to bed, temporary sexual liasons, practices that dishonour their bodies, or to use precise English: fornication, adultery, sodomy, etc. In daily practice they are reducing what should only be one of the finest aspects of humanity--the expression of true love--to careless gratification, to superficial entertainment, to abuse of others, to abuse of self.
'Abuse' is bad usage. Sexual abuse is bad usage--physical bad usage and verbal bad usage--of the parts of the body that make us and mark us as male and female. Everyone who manifests any form of abuse toward them is part of Roast-Busters Incorporated. In short, part of everyday New Zealand.