How do we know we aren't being brainwashed from the conservative perspective?

A: You don’t.

First principles critical thinking around apriori thinking should always shape worldview.

Aposteriori thinking around presented facts shapes response out of necessity only.

Limit mediated response to a lesser role than observed reality.

It’s why I always try to remind people, including myself, that I could be a bad actor (Don’t think anyone is deluded about themselves? Matthew 7:23). I do my best to get things right, and be honest, and pointed toward righteousness, but that doesn’t mean you can know that’s true, and it doesn’t mean I was right about any of it.

Imo everyone should be in that mindset and constantly testing everything (2 Corinthians 13:5, 1 Thessalonians 5:21). I’m just some non-authoritative pile of text on the internet, maybe good, maybe not, the Authority must always remain God.

2 Corinthians 12:9