They HAVE denied entry to quite a few people with legal status. Even if you are the holder of a VALID visa they can still deny your entry. This can even be done on a "Hunch" that you plan to overstay your visa. A close friend of mine had their valid visa revoked and was removed because they traveled into the US with an open return ticket. No harm meant, this person was backpacking and just trying to leave their options open. Quite frankly, anyone who was wanting to stay would just book a definite return and "forget" to show up at the airport that day. It shows the arrogance of our sworn "defenders" when they assume everyone traveling into the US is doing so to migrate. I have even heard of non-citizen legal residents being detained and removed by USCIS. With all the insane, one-sided and hypocritical immigration laws, the last thing we need are glorified security guards (who may or may not be influenced by their personal political views) enforcing said laws.