The Four Stages of Cruelty
The Four Stages of Cruelty as depicted in 1751 by William Hogarth begins with the torture of a dog as a child. Then the series progresses to beating a horse, to robbery, seduction, and murder in the final Cruelty to Perfection.
Yes, early animal abuse too often leads to murder or some other serious criminality in adulthood. It is both well documented and proven. Research it, by all means.
But what about the abuse of chickens, cows, pigs, sheep, and other animals raised explicitly for food?
Many of those who work the kill line in the slaughterhouses, and I suspect others in support of the business, go home to abuse their spouses and children, some go further, on to murder. 
A mentally healthy person recognizes the ugly doings of animal slaughter and can appreciate the psychological effects such may have on the committing individual. This psychologically sound person might even consider themselves cruelty-free. I understand this in the context of technicality and legality; they are certainly innocent of any unpleasantness or wrongdoing in that regard.
Now, I assume most readers see animals as sentients who understand pain, suffering, and fear death by brutality. If this isn’t you, goodbye.
To the others I ask, can proxy association to animal slaughter have adverse effect on the individual, on society?
Are there subliminal consequences suffered by granting passive authority to the animal holocaust?
Spiritual ramifications, to the so inclined?
If not, we may, in good conscience, pursue our struggles for equality while we passively encourage the inequality of our fellow earthlings.