VRB: Why is Lincoln singled out when millions of lives had been ruined under all the presidents until then, even the ones that libertarians honor …

I can’t speak for libertarians as a group, but I am a libertarian and I can’t think of a single President of the United States that I “honor.” I happen to think that all of them were perfectly repulsive, and those who preceded Lincoln deserve special contempt, both for their ongoing use of Federal bayonets to enforce fugitive slave laws and protect Southern slavers from uprisings, and also for their repeated forays into ethnic cleansing and genocide against American Indians. Other libertarians, especially those who are minarchists rather than (like me) anarchists, might be somewhat less sweepingly harsh. On the other hand, they’re also likely to be somewhat less harsh towards Lincoln in particular.

However, the reason that Lincoln’s under discussion at the moment, rather than every other President in U.S. history, is that the post is about secession and the U.S. Civil War. Since Lincoln was President during the U.S.’s largest-scale secession crisis and during the U.S. Civil War, it makes sense to discuss Lincoln, but going on about how I loathe and despise most or all of the other Presidents in U.S. history would have been somewhat off the topic.