Did they just not read the manga or even watch the anime?
Pain got genjutsu'd
Obito was in a drawn out genjutsu battle with Kakashi where they were both genjutsuing eachother
The only genjutsu resistance that the rinnegan has is applicable against other rinnegans but that's literally it
And even worse, is I've seen countless Naruto fanboys take this^ out of context and say that Sharingan/Rinnegan users can resist things like Kyoka Suigetsu or Kinshara Butodan when illusions DOES NOT EQUATE to complete hypnosis or empathetic manipulation that directly target and manipulate the soul