The principle of equality, as the exercise develops, states that everyone should be able to access to the same facilities and to each other. The quote shows said principle: it is unjust to treat people differently in ways that deny to some of them significant social benefits unless we can show that there is a difference between them that is relevant to the differential treatment. Different access to facilities, social benefits, social treatment, etc. should not exist as everyone is equal.
The main thing to understand from the principle of equality is that everyone is equal and no one should be treated as inferior or slave that is to say everyone deserves to be treated equally for instance now everyone should be given equal welfarism and everyone deserves to be given equal opportunity to showcase themselves. Equality means that there should not be discrimination against gender, race, and so on.
