I remember the first time I committed an act out of sadistic urges. I was 15.
I was minding my own business, out on a walk, and this guy was smacking his dog with a cane for no real reason. I got this uncontrollable urge and I ran up and slide tackled the man to the ground. I kicked him in the stomach so he was winded and disabled, then I took the cane and lashed him probably over a 100 times, listening to him cry in pain. I enjoyed his suffering. "How do you like being the abused now you worthless c**t". I gained a lot of pleasure from it. Every blow was like a rush of Ecstasy.
I didn't necessary feel empathy for the animal, but I don't see humans as superior to animals, and feel angered when I see humans abusing a form of life that deserves rights to live just as much as they do.
Since this incident I've felt a new side to myself. I don't seek pleasure in the suffering of any human, but certain individuals really do need a good belting, and I enjoy administering them, but I rarely do it now because I have a career to look out for and I'll get terminated if I get caught.
I haven't explored my sadistic urges sexually with anyone yet, which is why I hope to meet a good masochist some day. But I think sadistic sexual pleasure would have to come from a willing partner and it is different to the uncontrollable urge I feel to injure certain people and watch them suffer.