many Border Patrols don't really interact with regular US citizens on the border so I'll say they are biased against brown people its built into their job day in and day out.

Ignorance of the law is no excuse. There is a use of force paradigm that is a federal standard which is also enforced at the state level and every peace officer and agent is trained and tested on that standard as part of the licensing requirements in their state. If they violate those standards and commit abuse of force they can be charged with conduct unbecoming a peace officer as well as abuse of force or even aggravated battery depending upon their actions..