Solved
Remove user from security group
How do I remove/delete a user from a security group within ACS?
I have removed the user from the Product Profile in Admin Console, but the user still shows in the security group.
Adobe documentation says:
"If users are removed from a security group in the Admin console, they will remain part of the Adobe Campaign security group and will no longer be able to log in Adobe Campaign. In this case, remove the users’ email addresses in the admin console to prevent them from receiving sensitive information."
But it doesn't say how to remove them from the security group.