This dude is completely off his rocker - screaming like he just snorted a line of corn starch!
Funny how he changed his tone of voice when the G&F showed up. You boys did nothing wrong in my opinion. You didn't have to contact him "out of courtesy", stop and talk, offer him beer, cheese curds, fish fillets, etc. You got permission from the proper landowner and that's what its important.
At first I thought you guys were downwinding him and pass shooting birds feeding in his corn, But he actually just got done harvesting the corn and there were no birds in "his corn".. Its obvious this guy wanted to sit right on the field edge of the beans and corn as well and most likely shoot birds in the beans.