Now now, tempers.
Carnivorous, speaking as someone who's generally recognized for having an outstanding vocabulary, and for whom English is his native language, it never occurred to me that blackguard was anything more than a compound word consisting of "black" and "guard." It's a natural assumption for anyone to make, especially, dare I say it, people for whom English is their native language. As a fallen/evil paladin, "black guard" sounds like an entirely reasonable title. Black has pretty much always had the connotation of evil, darkness, fear, unholiness, etc. Guard makes you think of a protector or enforcer. Hence, to a native English speaker, when one hears the term blackguard applied to a fallen paladin, the term is almost synonymous with "unholy champion."
Back on topic, I don't know what I'm going to do as far as pronunciation goes. I've been aware for a long time of the existence of "justiciar," but the term "justicar" seems so prevalent that I'd always assumed it was a proper term.
I've noticed in the many, many, many pronunciation debates on this board (drow: rhymes with sew/cow), everyone always thinks their way of pronouncing the word sounds cool and the other way just sounds dumb. It's my suspiscion that, consciously or subconsciously, when people say "dumb" what they mean is "awkward and unfamiliar."*
I'll probably stick with justicar, because it's ingrained into me and justiciar is both awkward sounding to me and difficult for me to pronounce. Along the same lines, I'll probably write it as "justicar" because, as long as I'm pronouncing it wrong, might as well be consistent.
*As an aside, in the absence of anyone else to pronounce it, I'd long assumed that phlogiston was pronounced with a hard G, i.e. "FLOG-i-ston." In my last gaming group I encountered others saying the word for the first time, and they pronounced it with a j sound, accent on the second syllable, like "fluh-JISS-ton." It sounded really screwed up to me, but now that sounds more natural to me than how I used to say it.