That's exactly where systemic discrimination originates.
Hardly anyone wakes up in the morning and decides that it's a good day to oppress G people. They wake up in the morning having some amount of privilege, discover that it might be threatened, and their actions that day try to avoid reduction of privilege, even if it means treating G people unfairly. It's not anti-G people at first, it's just pro-self.
Over years this becomes a de facto systemic discrimination, generally without a rule that explicitly says "we don't want G coworkers". Instead there are rules that mean that everybody works on G holidays, the microwaves can't be used for "smelly" food (and guess what, all G food is "smelly" by default), and of course, rule is by seniority in the company which just happens not to have any senior G people in it. Somehow fewer G people get hired, and those that do are in low-status positions.
You can pick your own value for G; it could be gender or nationality or ethnicity or religion or skin color or whatever. It works the same way.