Divide and conquer, a regular phrase, a Twitter quote, but it is still used and it is effective. The reason it is still effective is, the participant of any one group or unit do not recognized its traits and characteristics.
To divide is to add to the belief misinformation to convolute the conversation. When the conversation becomes strenuous it descends into confusion, hurt, frustration...even physical death.

To divide and conquer is an old strategy that is still used effectively against groups if any kind. Just look in the public sphere