If a bike is tuned right it should be absolutely fine revved out. After all, looks at many 2 stroke sleds. There is absolutely nothing wrong with reving a 2 stroke out. However, there is some longevity/reliability to be gained with gearing the bike so the motor only revs to where peak power is.
The real problem is guys who are afraid to keep the bike opened up while keeping it pegged at top speed. Think of it this way. Your motor gets it's lube from the gas/oil mix from the carbs. Now you rev it up and get it maxed out at say 70mph on a long dirt road. Your in 6th gear wide open, then you start feathering the throttle yet keep the bike going at that same pace. That means the motor is still free spinning at that RPM, if you keep letting the carbs close yet keep it spinning where is the lube for the motor coming from?
Keep it opened up if it's revved up!