- Do you tell population a and population b contradictory things?
- Do you spread what you know is misinformation?
- Do you attempt to manipulate someone into working against their own interests. For example tricking a population whose interests and preference can best be expressed as A over B over C into voting for A so that C can win.
- Is your messaging a net harm to society? Deliberately playing up racial tensions to both sides determent for votes seems to fit the bill.
- Are you actual intents hidden because your interests are actually at odds with your target and they would act materially different if they understood your actual motivation?
The democratic usage of data appears to be primarily based on figuring out who could effectively message and the republican usage seems to be figuring out who they could manipulate and harm.
It's not that hard to see the difference.
What I find rather funny, were you to ask a Trump voter you'd likely hear them say the Democrats are the ones running divisive, racist campaigns, and that they've previously pioneered digital advertising in the political space only shows their pot-kettle policies in regards to the successful Trump campaign.
Either harvesting people's data and using it to message to them is a problem or it isn't. The message being sent is a distinct issue.