As to your second point, it's probably true that his views do dovetail with those of libertarians on many occasions, but supporting states' rights is guaranteed to set up a wedge between himself and libertarianism at some point.
Why is it guaranteed? Even many people in the libertarian party support states' rights. Like everything else, it's not an all-or-nothing. I've known Catholics who don't believe in the dogma that children who die before baptism don't go to heaven and it hasn't set up a giant wedge between them and their priest.
Well I don't mean that state governments will completely oppose libertarian principles if they had more power, but neither will they completely favor them. States could end up imposing legislation on issues like gun control, marijuana etc. that's just as restrictive or even moreso than the federal government which would leave libertarians pretty disappointed. I don't see state governments acting much differently from the federal government if they were to be given more power. But then again, it really depends on what the majority in each state votes for and who's in power in each state. As to my example, the marijuana prop in California could be seen as an assertion of states' rights given the fact that federal law probably doesn't allow the state to even put it on the ballot in the first place, but it failed anyways because the majority opposed it.
I've been busy with interviews and forgot all about this, so here's my belated response:
1) It is better to have some states have laws removing the ban than to have the entire country issuing a ban.
2) Asserting states rights removes the federal government's power in regulating this. That is definitely within the realm of libertarian thought: removing a strong power that a big government has used as a fist.
And keeping the notion of states rights also tends to support the very foundation of our constitution that each state is its own sovereign region with self-determination; our nation started out as a loose affiliation which has repeatedly become less so arguably because of the federal government jumping in.