... is saying mean things about them.
We've seen a good deal of this in the US with establishment politicians... no names mentioned because their allies will reflexively defend them. They get criticized and the politicians have no one they can strike back at... which for much of the establishment is their default response to attack. They either ignore it or undermine/put pressure upon the people that did it.
The recent abuses of federal bureaucracy to attack political rivals should highlight the danger of giving politicians this sort of access. They could for example trigger punitive tax audits or start burdening political enemies with hostile regulations.
This is not new. Politicians have done this sort of thing for at least a hundred years in the US alone.
The anonymity takes away their ability to hurt the people criticizing them which increases the likelihood that they'll be forced to simply respond to the criticism directly.