>Jews were also historically discriminated against

And Jewish people are a protected class, even defined by SCOTUS as a race for purposes of Civil Rights/Anti-discrimination laws

Why should historical discrimination matter to the policy? If at all, it should be about discrimination today.

Ummm...because historical discrimination has led to an environment where educational resources are unequally distributed? The effects of those historical policies still exist...and they should therefore be taken into account today...since they still exist...the effects...

Let's say that your parents were discriminated against, and were unable to go to college, or find a good job, or were actively lynched due to their race.

Do you think their kids might be affected by say, the economic troubles their parents might've gone through, or the fact that they lost family due to the racial animus at the time? Or how about if those families were relegated to places designed specifically for them, to keep them away from the rest of the populace, with less opportunity for education or work. Do you not think that might have a multi-generational effect?

It's simpler than that. If legacy status can influence your ability to enter university, then whether or not your parents were barred entry has a direct effect on whether or not you will be able to get in.

Because Harvard admits on legacy status.

This is unrelated.

No it is not.

If Jews have had a hard time getting into Harvard in the past, and Harvard uses legacy status, then that means that Jews will.habe a harder time in the future for getting into Harvard.