I think this is the fault of the crowd, not the capo. When a song is off beat, or off pace, I first look to the capo and try to sync with him. If that fails I go with predominant pace of crowd. If the capo is gesturing to clap or moving his hands to dictate speed, it is easy enough to see. Most people don't look to the capo and just sing at whatever speed they think is correct. Either because they are watching the game, or just don't care. IMO the section often goes way too quick on many chants, sometimes it gets ridiculous.