Flat response in plugs is not nonsense simply because Fletcher-Munson curves already exist. Good plugs eliminate an additional layer of unwanted frequency disto

Flat response in plugs is not nonsense simply because Fletcher-Munson curves already exist. Good plugs eliminate an additional layer of unwanted frequency distortion in the audio that you're hearing. Yes, Fletcher-Munson effects can change our perception of frequency response. But that doesn't mean that we should tolerate additional negative effects. That's like saying that we shouldn't stop the cook from using too much salt in our dish because the chicken is already dry. Clearly it's preferable to have chicken that is ONLY dry, rather than chicken that is both dry AND over-salted. Don't be so dismissive about people seeking a good audio experience. If you're at a concert there's a lot of factors that are out of the audience's control, but good earplugs are low hanging fruit if such things are important to them. And if you're the musician on stage cranking an amp, using cheap ear plugs is going to create a disconnect between what you hear and what your audience will hear. If you have to dial in more top-end to compensate for the dulling effect of the plugs for your amp to sound "right", then your "right" sounding amp setting will be perceived as harsh for the people in the audience who aren't wearing plugs. Finally, if you're at a rock concert (with a sound engineer mixing the band) the engineer will be hearing the concert at the same volume as you. They will already be balancing the band's sound in a way that compensates for the effects of the Fletcher Munson effect that you're concerned about.