AFAIK, Libertarians are not Utopians. If there is a choice, they prefer decentralization and secession. Underlying reason is not important (Ethnic and religious, or ideological).
Besides, from what I know, in large sovereign states and large democracies minority or ruled ethnic and religious groups always suffer. Because they will be imposed the ruling groups culture, language and curriculum. If they want, they should have at least a degree of self control and identity.
Eh all other groups want the whole country and the other groups pressed to geno-cidere?
Thats not a ideology thing, that is more a "Real-Politics" that worked with pakistan and india - kind of approach.
Except for the Kurds, that doesn't seem to be want the groups in Iraq want. I wasn't aware that libertarians were generally in favor of imposed religious- and/or ethnicity-based balkanization against the will of the people.
I suspect that would actually work against libertarianism, also, because greater ideological uniformity in the constituency would support more authoritarian government (light touch is a way of accommodating divergent interests which would be eliminated).