We perceive social justice through a prism of intervening considerations, like how much:
...people have control over their circumstances
...luck figures in life outcomes
...the rules of the game are fair
...people deserve what they get
Another consideration is what we think people are entitled to. While deservingness is conditional on some action or (de)merit of the individual, entitlement is more about laws, norms and rights. Some entitlements are uncontroversial, like the right to a public education or trial by jury. Others are contested, like the right to reparations or healthcare. Disagreements about entitlements are often accompanied by expressions of contempt, moral outrage, and/or grievance.
Although social justice narratives seem to rely on assumptions of entitlement, social justice activists may avoid the actual word "entitlement" (or variations thereof) because of its negative connotations, as in "culture of entitlement". It doesn't help that people with a strong sense of entitlement seem rather unlikable. Indeed, several studies have found that strong personal entitlement beliefs are associated with rather unpleasant traits, such as selfishness and lack of empathy.
Reference:
Tomlinson, E. C. (2013). "An Integrative Model of Entitlement Beliefs." Employee Responsibilities and Rights Journal 25(2): 67-87. https://link.springer.com/article/10.1007/s10672-012-9208-4