If the sight of a fully-grown man’s bare arse bathed in blue LED light has you shuddering with disgust, then you simply aren’t acculturated to the ways of Metal. If you are willing to sit through songs detailing gruesome acts of murder and purchase merchandise emblazoned with decapitated infants, but you suddenly become grossed out as a lead singer’s testicle peeps at you momentarily from its loin cloth, you’ve got a long way to go, kid. Impetuous Ritual’s performance in Dublin earlier in the month raised a few questions about the visual effect that nudity has on the overall presentation…