Earlier quoted context omitted.
I've been through many times as white British person (both as a visitor and on various visas) and have never had a bad experience. I'm not denying that people do have bad experiences. But I find it kind of hard to believe that as a US citizen, you've never once had an experience of re-entering the country that didn't involve the customs agent asking you a couple of simple questions and then sending you on your way.
Since they have to let US citizens in, you likely don’t have to answer questions unrelated to the goods you’re bringing back. But the pressure is obviously there to answer anyway.
(This is in contrast to interacting with police within the country, where they can’t search your stuff against your will or hold you without probable cause, and not answering questions is a good default.)