In all honesty, it was probably a little of both. He was naive and he overlooked more than he should've because they were kind to him and he admired their knowledge and skill. If Arima hadn't come when it did, Harry can admit to himself that he would've tried to pull away.

Being thought of as an idiot is preferable to knowing better and not doing something about it.

Harry nods and after a moment casts the charm. His patronus is bright and defined enough so that the feathers flutter and move in an invisible breeze. He looks at the barn owl for a moment with a strange expression and then sends it off with a message. Remus, can I trouble you with something?