Unfortunately you cannot hide/remove those.
Reason: They are not usual views, they are part of System tailored Activity entity family (Activity, Activity Pointer, Activity Party, Custom Activity types, etc).
If you see any Activity entity properties, the checkbox 'Display in Activity Menus' is checked & disabled. This settings is being used for navigation, views, filters, etc.
Even while creating custom activity, this option is enabled & if you forget to check it, that particular Custom Activity type will be hidden from everywhere wherever you are using its siblings (Email, Fax, etc)
If its unchecked, Even Associated view will not be showing this activity under it's regarding Parent record, which is failing the main reason why we are using CRM & activity relationship.
In a nutshell, this setting once enabled, cannot be undone. The activity cannot be distinguished/disabled using security role, because all are of same bucket.

Maybe you can try some unsupported customizations using DOM explorer in javascript & hide it, which I don't recommend. PowerObjects blog talk about renaming it to something to avoid users using it & other options.