I am no Constitutional Attorney, but it is my understanding that states, counties, cities etc also must pass Constitutional muster when passing ordinances. For example, a little town in Georgia cannot pass segregation laws making black folks sit in the back of the city bus. These entities cannot pass unconstitutional laws simply because they have been afforded more rights than the federal government.
They must obey The Constitution, yes, but nowhere in The Constitution does it give any explicit restriction of The States (the people) to self regulate their communities in a way as described in the OP. This is the intent for the 9th and 10th Amendments.
Jim Crowe laws are Unconstitutional because there is now a Constitutional amendment forbidding them.
The history behind the so-called Jim Crowe laws is actually a pretty decent analogy for what we have here. If Jim Crowe laws were once again Constitutional, you might have a small few states adopt them. More than likely, just about every State would make the laws unconstitutional (small u) under their own state constitutions. Jim Crowe laws wouldn't exist today not as a function of The Constitution, but simply as a matter of popular sentiment.
The same could be said about singling out supposedly "goth" kids and placing a curfew on the basis of sub-culture fashion and lifestyle choices. If the idea that discrimination in this manner isn't popular then communities will lift the applicable ordinance(s) and States can make such actions unconstitutional.
It is not the right or the function of the Federal Government to legislate morality in this manner. The Constitution is specifically silent on such matters so as to allow The States to choose. The idea being, your state is something you affect more directly and is more of a local community. Just like bigotry amongst a small community such as the Westboro Baptist Church is the right of that community, The States are restricted on very few things in the context of The Constitution and can specifically address in detail matters as the one in question in their own constitutions (small c).