You know that thought experiment where you have scientists debating global warming, but to make it clear just how much consensus there is, instead of having 1 scientist against and 1 pro, you have 1 against and a whole crowd pro?
I run this thought experiment every time I enter the states. I can usually see around me many thousands of people in the airport, getting along just fine. I can imagine the many tens of thousands who go through those airports every day, and the probably millions all across the country who go through the airports without trouble.
These millions are what you should be stacking up against the dozens of anecdotes you get on the web.
(For what it's worth, I have had very easy experiences with immigration, with mostly people being very nice to me, but a few times someone was rude/mean to me. Nothing more than that.)