The Marsh Pit is a long forgotten element of the 1990s. It was offensive at the time to everyone and persisted for some years.
The idea of the Marsh Pit was that a "Grudge Band" would play grudge-oriented music. This sounds good, because I do love holding grudges, but I can't understand the words when they are so loud. Regardless, they would set up these dirt pits around their shows and people would fill them. Not regular people who worked in business, but filthy people with cheap shirts and pants who lived in bus stations. They would gather in these pits and bang into each other, rub against each other, and carry each other through the air. The music would be loud. People would be farting and sweating. And so, the pits would get very swamp-like or "swampy" in the current Internet parlances. So, they became known as marsh pits. The people who danced in them were known as "greasy wigglebutts."
Sometimes the bands would get into the marsh pits themselves. It was disgusting. One time my Pontiac broke down due to foreign mechanics working on it and it was near a marsh pit. I went to find a phone and came upon these half-dressed, muddy people covered with piercings and tattoos and they were writhing around and moaning. I couldn't take it.
These times are over but are part of the sad history of when this nation went off the rails, but today we have stuff I can't get a handle on it all. Ban it. Ban it all.