Robert, with great respect, I think you miss the point of the footnote. The point is not to say "I will perpetuate the mistake" but is, in fact, "in order NOT to perpetuate the argument" - I have always called them seamen of the guard in conversation or writing when I have not used the French original. My argument is not so much what they were called - I don't have an issue with that and I get rather tired of continual to and fro semantic silliness - my issue is the way in which they were used.
This is, perhaps, one of those issues in which the French title would have done better in the title - except for one fact. Do you want to try explaining to the order clerk at Barnes and Noble that the book is titled 'Marins' not 'Marines' and it's 'Marins de la Garde' to boot? You'll be lucky if the book you receive doesn't turn out to be a pocket guide to Marha's Vineyard. That's why in my experience of almost 30 years in publishing it is best to leave the development of a title and commercial package to the people who do it for a living and I try desperately hard not to influence their thinking. After all - if they get it hoprribly wrong - I can blame them!