The government is allowed to mess with cokes recipe because we don't want it to be too bad for people's health. I don't see why we shouldn't mess with algorithms to protect our personal and national health
Democracy needs to protect free speech. Part of that is keeping the information "playground" equal and fair. Fighting disinformation and protecting access to the press is important for that.
A well informed population is vital to prevent the masses from being dragged along by some rich guy just buying a common social media platform