The Restlet class
logs a warning in case a DELETE method call is performed with an entity, indicating that "The current DELETE request provides an entity that may be not supported by the Apache HTTP Client library. If you face such issues, you can still move to another HTTP client connector."
Unfortunately it seems impossible to force the Camel Restlet module to prepare a DELETE Restlet Request with no entity. In fact the class
org.apache.camel.component.restlet.DefaultRestletBinding in its method populateRestletRequestFromExchange always creates an entity. Instead it should set a null entity in case exchange.getIn().getBody() is null.