There are a couple of problems with that idea.
The first is that PD has long been applied to "classes" of beneficiaries.  Eg:  older, white, middle class women are treated very differently by police officers that are scruffy adolescent males and black males in general.  In the immigration context, it's long been accepted to treat entire classes of people differently.  People who have USC children, eg, are more likely to be released than people who do not.  These are just two examples that come to me off the top of my head.  When I retire, I will have the luxury of more time to think about such stuff -- :-).  
 And who is it that has decided that PD is not to be applied to a class of people?
Despite the popular beliefs among those who know very little about DACA, but still oppose it on principle, DACA is not a wide open net that catches everyone.  There are specific and limiting requirements; many young people are excluded.  
Continued