A wheel adaptor isn't "right" or "wrong". It's a piece of metal. It bolts to your existing wheel studs, and carries another set of wheel studs to bolt your rim to. As long as the metal that the adaptor is made from is strong enough to carry the forces placed on the studs, it just widens the track width and possibly changes the bolt pattern. That's it. Wheel adaptors are run on all kinds of applications, and as roccodart440 pointed out they're used by default on all dually applications. There's nothing inherently "wrong" about them, so not using them isn't "right".
If you use quality parts and torque them as specified, there's no issue. I prefer to have my wheels fit without adaptors simply because I don't have to bother to check the torque on another set of lugs that happens to require taking my wheels off to access, but that doesn't make using them wrong or unsafe.
