The חשק שלמה asks the following question: what does the gemara mean by saying -- what should we do to prevent lashon hara -- its an aveira! so use your bechira chofshis and then you won't sin! To answer this he quotes from the shut בית שמואל in a drush on parshas metzora:
The gemara in בבא בתרא says that lashon hara is an aveira that a person cannot be saved from daily.
Maharsha there asks -- if we cannot be saved from it, why punish us?
To answer this (in a different direction than maharsha there), he suggests that it is correct we have no real ability to be saved from it unless we use the solutions presented in the gemara, to involve yourself in learning or to be mashpil yourself to save yourself from this aveira. And the punishment for lashon hara is for not using this remedy. This is the reason why this specific aveira has a takana suggested for it.