No-one here is saying it should have been a red but there are posts in this very thread raising the question, one of them from you yourself, in addition to plenty of discussion in the media.
As for the question of petulance: it could have been, but it could equally well have been some momentary panic with no particular intent. I doubt Nunez himself knows what goes on inside his own head half the time, so I wouldn't want to try and read his thoughts from outside. The fundamental question is whether such enduring immaturity is acceptable from a Liverpool player, and there I suspect most of us are in agreement that we need better.