Oddly enough, I do see this among my own friends. Outside of this community, among my circle of friends, those who tend to favor VII more than say me, tend to also strongly dislike IX with a passion, whereas the opposite is true concerning IX lovers not liking VII. Course most of my friends are self-proclaimed line artist and most of the issues stem from the art direction but whatever.

Personally, I feel the real rivalry is VI vs. VII, whereas IX tends to be overlooked cause it doesn't have the same PR as VII and X or the controversy of VIII going for it. There is certainly a healthier IX fanbase on this forum, but not so much elsewhere that I've seen. I think the surge of popularity VII brought to the fanbase as well as more obnoxious elements of said fanbase back in the day (most VII fans are pretty chill nowadays) probably gave a lot of resentment towards the rest of the fanbase, which is why you'll often see the game get picked on far more often in non-VII focused parts of the internet unless the topic jumps to a more controversial titles like FFII, VIII, and every post-FFX entry.

Oddly enough, I've been seeing this a lot more in the professional critic community as well since often top RPG lists tend to downplay VII more lately and often gives more credit to other titles. Not sure if this is pure backlash against the game or people finally trying to look at VII more objectively, both sides of the argument will likely jump to their conclusion and stick with it.