You can uninstall or removes an installed erlang-diameter package itself from Ubuntu 16.04 LTS (Xenial Xerus) through the terminal,
$ sudo apt-get remove erlang-diameter
If you would like to remove erlang-diameter and it's dependent packages which are no longer needed from Ubuntu,
$ sudo apt-get remove --auto-remove erlang-diameter
If you use with purge options to erlang-diameter package all the configuration and dependent packages will be removed.
$ sudo apt-get purge erlang-diameter
If you use purge options along with auto remove, will be removed everything regarding the package, It's really useful when you want to reinstall again.
$ sudo apt-get purge --auto-remove erlang-diameter