Nobody likes rubbish or lazy footballers on their team. The trouble with booing is that it effects everyone. It indiscriminately undermines confidence. It's purely destructive and does nothing to specify what you're unhappy about. It's like a baby's cry - it will cry when its hungry, scared, got wind, uncomfortable, filled nappy etc. The reason we learn to talk is to be better able to specify what we're unhappy about.
Remember the clip when Poor dim old Ross Barkley had to be told by Jags who the crowd was booing? Being told is one thing, but believing that is another.