SharePoint 2013: JavaSript Object Model - Inserting 'Reusable Content' programmatically not working

Question

Goal: I am trying to click a button on a page that sets the 'PublishingPageContent' field on another page with data from a 'Reusable Content' list item.

Problem: Whenever I go to the updated page and check it's source via 'Edit Source' in the ribbon, the span tag that holds the reusable content is stripped down.

Here is my code:

var pageContent = '<span class="ms-rtestate-read  ms-reusableTextView" id="__publishingReusableFragment" contenteditable="false" fragmentid="/sites/testpublish/ReusableContent/4_.000"></span>';

I then set the 'PublishingPageContent' field to pageContent.

Now when I go my updated page, the reusable content is not showing up and it's stripped some of the code out when I view it in 'Edit Source'

Here is the code in 'Edit Source':

<span class="ms-rtestate-read  ms-reusableTextView" id="__publishingReusableFragment"></span>

Any idea why this is happening? Thanks