When I use the term "grognard" it's only for people who are so enamored with their personal favourite versions, that not only they refuse to progress to the next edition just because it dared to change something (then I'd just not like them for stagnation-ism), but also impose their own personal views on everybody else. Like:
A: "PHB should have only the Tolkien races because they're the classic D&D"
B: "Why should we only have the 'classic' races?"
A: "Because they're classic, dumass. They - and only they - should be there because that's where the game started."
B: "Yeah, and we progressed since, and have some actually original and interesting races."
A: "I don't care, only classics can be in the core."
B: "Okay, so you will have classics in the core AND I will have my 'freak' races. So we both can play what we like."
A: "NO BECAUSE MY PREFERENCES TRUMP EVERYBODY ELSES PREFERENCES AND ONLY WHAT I LIKE CAN EVER BE IN THE CORE"
That's a sample of what I call a grognard. Person so stuck-up in their personal, archaic preferences, they're actually willing to take content away from other people because of some misguided sense of "classicity" and "traditionalism". And that's why I'm "anti" them. Because they're harmful to my style of play, by (intending to) removing options the game gives me.