I think we all need to remember why we watch sport, and thats to enjoy it, enjoy the really good moments as they don't come round very often. Beating your local rivals in the 30th heat of a semi final should absolutely be savoured.
The riders will know that they need to go again with that same intensity of the final. If that doesn't go to plan and they'd held back on the good feeling of the semi final then its celebrations wasted. I'd never criticise any team for celebrating any win in any sport, as long as opposition fans aren't being goaded. Enjoy the smooth as there's plenty of rough which isn't as much fun.