I think that you don't want to change the object being passed to the method, So you have made a deep copy. And you want to return a new JSON object.

Am I right so far? If yes, As you have made the deep copy, use it, loop through each element of the array of your concern and replace the Node value with what you desire.

private static JsonNode attachmentConversion(JsonNode object){



    final String ATTACHMENT_POINTER = "/RESULTS/ATTACHMENTS/ATTACHMENT"; //Path to the array
    ObjectNode OUTPUT = object.deepCopy();
    OUTPUT.remove("DETAILS");

    //Validate is an array - It properly fetches the array
    if(OUTPUT.at(ATTACHMENT_POINTER).isArray()){
        int counter=0;

        //Loop through attachment array - It properly fethes each object in the array
        for(final JsonNode objNode : OUTPUT.at(ATTACHMENT_POINTER)){
            ((ObjectNode)objNode).replace("ATTACH_CONTENT", xmlToJson.parseXmlToJson(objNode.get("ATTACH_CONTENT"));
        }

    }
    return new ObjectMapper()
            .createObjectNode()
            .set("customertopology", OUTPUT);
}

I haven't tested this, but I think something like this would do what you want:

import org.codehaus.jackson.node.ObjectNode;
// ...
for (JsonNode personNode : rootNode) {
    if (personNode instanceof ObjectNode) {
        ObjectNode object = (ObjectNode) personNode;
        object.remove("familyName");
        object.remove("middleName");
    }
}

You could also do this more efficiently using Jackon's raw parsing API, but the code would be a lot messier.

How about something like below. You can directly read a path and depending upon that delete a node. No need to loop all keys.

String tt = " {" + 
            "      \"experience\": 14248," + 
            "      \"hitpoints\": 9223372036854775807," + 
            "      \"name\": \"Aaron1\"," + 
            "      \"uuid\": \"78edf902-7dd2-49a4-99b4-1c94ee286a33\"," + 
            "      \"image\": {" + 
            "        \"@type\": \"blob\"," + 
            "        \"content_type\": \"image/jpeg\"," + 
            "        \"digest\": \"sha1–4xlj1AKFgLdzcD7a1pVChrVTJIc=\"," + 
            "        \"length\": 3888349" + 
            "      }" + 
            "    }";
    ObjectMapper mapper = new ObjectMapper();
         mapper.enable(DeserializationFeature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT);
         JsonFactory factory = mapper.getFactory();
         JsonParser createParser = factory.createParser(tt);
         JsonNode actualObj1 = mapper.readTree(createParser);
         JsonNode path = actualObj1.path("image").path("@type");
         if( path != null && "blob".equalsIgnoreCase(path.asText())) {
             ((ObjectNode)actualObj1).remove("image");
         }
         System.out.println(actualObj1.toString());