About the whole crowd reaction thing, where I was I didn't hear much booing. I certainly heard a lot of jeering though.
It's sixty thousand football fans at the end of the day. Cheap tickets too. You're bound to hear everything and anything. Football fans don't exactly hold a reputation for being the most composed group either lol.
When someone's played that shit they tend to hear about it.
I just so happened to have a direct sideline view of Jenkinson being completely ransacked by the Southampton midfield and left back in the first half. He was the closest player to the block.
When you see your player completely overwhelmed and positionally all over the place, making mistakes constantly which then leads to a goal, its only logical that it evokes various different reactions around the ground. As a very very small example, me and a friend were more in the 'wow fuck me this is diabolical' facepalming camp than the 'oh for fuck sake he's so shit' brigade around us.