delete a fragment
Currently you cannot delete a fragment. However you can change the audience part of a fragment definition to an expression that won't match any users so the fragment will not show up on any user's views. A recommended fragment definition audience is something like
<dlm:audience evaluatorFactory="org.jasig.portal.layout.dlm.providers.PersonEvaluatorFactory">
<attribute name="username" mode="equals" value="nonExistent"/>
</dlm:audience>