In fact, the query that you provided is supported. You should use the IObjectScope Remove method. It can accept as parameter IEnumerable or IEnumerator variables as well as single persistent capable instances:
var results = from items inscope.Extent<Product>()
where items.Discontinued == true
If the table, from which you are deleting records with the preceding query, is a parent table you can use cascading delete as well.
Additional information about the cascading delete option can be found in the following Knowledge Base article - CRUD example with Telerik OpenAccess ORM. There is also a demo project in the Code Library - Implementing cascading delete with Telerik OpenAccess ORM.
I hope you will find this information helpful. If you have any other questions, please do not hesitate to contact us.