It might have something to do with the fact that Ron is strongly pro-State. His ideas on State rights would allow individual states to decide on issues such as homosexual marriage, civil rights etc.
Like many libertarians, he is not a racist or a homophobe. However, his position would overturn the ability of the Federal government to enforce anti-discrimination legislation against the wishes of individual states.
States rights are good in theory but I would much rather see the protection of individual liberties. Historically, it has been much easier to achieve a majority in support of individual liberties at a national level than to achieve a majority in each of the 50 states. The flip side is that a majority at a national level can also be used to infringe the rights of individuals (even if particular states would have protected those rights).
For some reason, many libertarians are unable to see the trade-off between individual liberty and states rights.
Gurdur has spoken of this more eloquently than I in a thread about the civil war.