I think you are massively over reacting, the crowd have been quiet, borderline apathetic for most of the season, they are not used to watching fast exciting football with countless chances to score, they aren't used to battling, inspiring performances and nicking a goal to win, they aren't used to winning every other week.
They are used to not being excited, sacking Slav won't have anyone protesting or complaining on Sunday, unless the team produce more of the same, which proves its the players and not the managers or board