Rationing and price fixing cause hoarding. People hoard because they fear not being able to buy something in the future, which happens with the shortages caused by rationing and price fixing.
For example, back in the 70's with price controls on gas, people hoarded gas. All that nonsense stopped literally overnight when Reagan repealed all gas and allocation controls.
People hoard because they either fear the prices will get jacked up soon, or because they hope the price will get jacked up soon, so they can make a neat profit off of other people's desperation.
Anti-gouging and rationing prevents that hoarding, as long as they are implemented intelligently.
When people know the price won't increase wildly, and know that rationing means the shelves won't be suddenly empty due to hoarders, they will buy what they actually need and not try to hoard.
Additionally, since the price is kept manageable, everyone who needs the items will be able to afford them.
If you don't combat hoarding and price gouging, people will panic buy, because they know the price could increase at any point, and because the want to get ahead of the hoarders. Now they become the hoarders.
Libertarians fail to understand why businesses often do not extract the maximum possible profit from the market at all times, because they do not understand that commerce is much more complicated and human, and not solely based on supply, demand and price signals. They do not understand the business/consumer relationship. They do not understand morals and ethics, and why businesses would want to maintain a good relationship with the customer base, instead of fleecing them to the maximum possible extent.
For example, back in the 70's with price controls on gas, people hoarded gas. All that nonsense stopped literally overnight when Reagan repealed all gas and allocation controls.