U.S. Official Denying Entry

[kitkat1 5]

Gaining entry to the USA, with or without a visa, with or without permanent residency for that matter is discretionary. POE agents have the right to turn back a person even if they are bearing a valid form of identification and documentation.

True they have the right, and this most often happens in cases of people who cannot prove non-immigrant intent.

People who have valid immigrant visas, (whether or not they needed to go through the waiver process), and have not broken any of the rules (i.e. let their green card expire, stayed out of the country for beyond the allowed time, etc.) are generally allowed to enter. There's no reason for concern.