Did you tried as below?
1. Create a Security Group as "Email Designer"
2. Next if you click on that you can see the list of options like licensing,Interface access,Action permission etc.
3. From that choose default permission , this is for what are the activities the user can do when they create a Asset.
4. In the Email choose the permission you want to apply (it can be View , Edit, Delete secuirty)
5. Then for the Campaigns , under the Asset creator you can ensure that Activate is not chosen (View ,Edit, Delete, Security ,Activate)
Hope it helps