We speak the language and pronounce new words based on the past words of the language. There are exceptions but they don't negate the defaults.
Nearly every single word in English that starts with a g followed by a soft ih/eh vowel is pronounced as a soft g, just a few:
gin gypsy general gerund Gerald gel gem gyp Geronimo gesture
In fact, there are something like 20,000 words in the dictionary that start with G and the number of them that are pronounced with a hard G where this rule otherwise dictates a soft G is such a small fraction of them that it has its own wiki page.
This video is a tad harsh for comedic effort, but otherwise entirely fact based and sourced:
Bottom line: you're free to use a hard G, but it's not the default pronunciation based on either all other English words or the creator's intentions, and if you're confused why others pronounce it with a soft G, they would seem to be simply more familiar with the English language 🤷♂️
Nearly every single word in English that starts with a g followed by a soft ih/eh vowel is pronounced as a soft g, just a few:
That is patently not true and blatant cherry picking, e.g. already contradicted by the lexically matching word “gift” (and there are “giggle”, “gild”, “girl”, “git”, “give”, “gizmo”, etc.). See Wikipedia, which referenced linguists studying this:
An analysis of 269 words by linguist Michael Dow found near-tied results on whether a hard or soft g was more appropriate based on other English words; the results varied somewhat depending on what parameters were used.[11] Of the 105 words that contained gi somewhere in the word, 68 used the soft g while only 37 employed its counterpart. However, the hard g words were found to be significantly more common in everyday English; […]
All you basically said is "nuh uh because my feelings" and then an appeal to authority who disregarded the following vowel sound. "But he's a professor" proves nothing, let alone backs any sort of assertion that you or he are familiar with squat 🤷♂️