This is a confused article. > Most Romans ... thought cruelty to slaves was shocking but also > did not hesitate to punish their slaves, and to punish brutally. Floggings, crucifixions, torture by means of the rack and breaking the legs with iron bars would all be carried out in public to maximise the impact on the observers. Or a slave’s children might be sold off, never to be seen again. ... so, not that shocking?
If you want an analogy, today, most people have no problem farming animals to raise them for meat. There's a lot of cruelty inherent in the process, but we do try to take steps to reduce it. And if you outright enjoy the wails of pain from the cow as you beat it needlessly on the way to the slaughterhouse, there's something wrong with you. Just as to the Romans, beating your slaves and sometimes making an example might be necessary, but a slaveowner who took a little too much pleasure in it was morally suspect. It's telling that Roman histories are full of allegations of the capricious torture and rape of slaves by prominent figures. While some of these accusations are probably true, they are generally of a slanderous nature intended to tarnish the reputation of the accused.