So your argument is actually that people who pronounce it with a hard G have just never heard anyone say it.
And we're taking about dot-g-i-f, the format that is hugely shared as memes and as reactions in chats, a form so well known that it's at Kleenex level of awareness - awareness that exceeds itself - ie, all other variants of this format (apng, animated webp, even webm) are called gifs.
And you're saying that most people, which is, given the prevalence of gifs, probably most of our species at this point - most of the sentient life forms in our solar system are aware of this format's name... But we've just never heard anyone say it. Except for a small, vocal minority - who exist mostly on the Internet and are deeply online. Those are the only people who have heard it said out loud.
And, in that impossible scenario, most of our species - who have, again, never heard it said it loud - billions of people - all, independently, came up with the same, supposedly incorrect, pronunciation.
That's your argument? I feel like your case would be stronger without it.
It's like intentionally taking a Principal Skinner stance - everyone else on earth is wrong. Except, at least Skinner was oblivious.
There's simply no justification for the jif pronunciation. There's an explanation - ie, because the creator of the format wanted to float his success on the back of a peanut butter brand. And it didn't even work - no one calls it "jif" and yet it's probably got better name recognition than the peanut butter. But - even as weak as that explanation is, an explanation is not a justification. A justified pronunciation - even if it's different from the original pronunciation, is one people natively come up with, and yet is always the same.
Is that supposed to be an argument? That there are two ways to pronounce the letter g? I was actually already aware of that - even before I'd ever heard of gifs.