I wouldn't lend it much credence, but it certainly mattered where you were. The Home Guard in central NC wasn't the same thing as in East TN. There, and in Missouri, the politics and loyalties were much muddier, and things quickly descended into a civil war within the larger conflict. Champ Ferguson and Jack Hinson are worth reading up on (as is Woe to Live On- the book Ride with the Devil is based on)- they epitomize how fast and vicious things could turn when you're dealing with new and old blood feuds and political loyalties in the midst of the biggest war the New World had ever seen.
Personally, the I thought the HG got a bad rap in the book. Most of them weren't tyrants, they were regular, decent, guys who either physically weren't up to regular service or had jobs/responsibilities on the homefront that precluded a more active service. In most places, they were just trying to keep order and send deserters back. Given that they were human, and recruited from the human race, I don't doubt but that there were plenty of shitheels and bullies in the mix, but no more than is common than you run into with any group of 10 or more people.