According to GIMPS, this is the first time a prime number was not found by an ordinary PC, but rather a “‘cloud supercomputer’ spanning 17 countries” that utilized an Nvidia A100 GPU chip to make the initial diagnosis. The primary architect of this find is Luke Durant, who worked at Nvidia as a software engineer for 11 years
They literally told you how it’s used for practical applications and you just ignored it. It makes cryptography stronger, hence your password less likely to be broken. National secrets less likely to be leaked. Your identity less likely to be stolen.
I wouldn’t bother arguing with this person. They’re either trolling or intentionally ignorant - either way, you will lose to their vast experience.