I want to hide the [Phone] command of the [Activity] entity without any third party tools or XML edits.
These are unnecessary command buttons for users who don't use them.
Continually displaying unneeded command buttons is a hindrance to business efficiency.
If you can't hide it, you should be able to disable it so that it doesn't transition to the form when you click on it.
It is desirable that the user is free to edit the command bar, not just this command button.