There was a sharp transition in European society about 400 years go. Before then, burning cats alive was a popular entertainment and so was being a spectator at a public execution or a public torture session. If human psychology worked the way you say it does, then although it would be possible to reduce public displays of violence (e.g., if people opposed to it find themselves with much more power than usual) European society (and its derivatives, e.g., the US) would have a strong tendency to bounce right back to having high rates sadistic violent after a generation or two (because according to you, repressing the impulse permanently is futile). But that is not what happened. The most parsimonious explanation for what actually happened is that before 400 years ago, the high rate at which people (and particularly impressionable male teenagers) were exposed to sadistic violence greatly increased the desire of the average person for sadistic violence in a self-sustaining cycle and that making it much less likely that boys and male teenagers would witness any sadistic violence greatly decreased the appetite for sadistic violence in the society again in a self-sustaining cycle.

> the high rate at which people were exposed to sadistic violence greatly increased the desire of the average person for sadistic violence in a self-sustaining cycle

Well yeah, everyone wants to belong and be part of the tribe. We conform a lot to societal tendencies. That's not what I'm referring to. I'm referring to the individual sadist with that as a core part of their identity, not an individual with an anthropological adaptation.