You might as well get over being angry. There is not a college or university in the country -- public or private -- that would not do, and does not do, the same thing as Notre Dame. Legacy admissions are how you build an institution's "family," thus encouraging future dedication to the school (a.k.a. donations). Moreover, existing contributions to a school are often rewarded.
Thanks to the fact that schools need donations and endowments to stay in the black, such admission decisions are part of the landscape of higher education. Is that fair? Well, can you think of any institution, company, or program in the country that would not reward loyalty and financial support? I can't think of any.
So don't be mad... it's just a fact of life.