The problem is that you have uncomposted manure in large quantities that can runoff leading to water supply contamination.
Feedlots are destructive to the environment in a way that rotational grazing is not. Grass fed beef with rotational grazing is good for the environment, reducing fertilizer requirements without causing food contamination or wasting resources trucking cows and grain around. It's not good for big-ag, because they need a market for their subsidized corn/soybeans and it's not good for national beef producers because they want to co-locate and integrate everything for cost savings, but it'd be good for the cows, the environment and local businesses that are being undercut by the national players.
Feedlots are destructive to the environment in a way that rotational grazing is not. Grass fed beef with rotational grazing is good for the environment, reducing fertilizer requirements without causing food contamination or wasting resources trucking cows and grain around. It's not good for big-ag, because they need a market for their subsidized corn/soybeans and it's not good for national beef producers because they want to co-locate and integrate everything for cost savings, but it'd be good for the cows, the environment and local businesses that are being undercut by the national players.