This quotation comes from Chapter 8. As Ponyboy sits in the hospital and watches Johnny dying, he muses on the fragility of group cohesion. It seems obvious that Johnny needs the greasers—he is small, passive, and poor, which makes him an easy target of Soc violence. Less obvious is the gang’s need for Johnny. The greasers need a vulnerable friend to give them a sense of purpose. Telling themselves that they exist to protect people like Johnny lets them avoid thinking about the fact that their poverty and vulnerability leave them no choice but to band together. Ponyboy comes to this conclusion at the end of the novel, as Johnny is dying. He understands Johnny’s value only when he is about to lose Johnny, which amplifies the pain of the loss.
Here we have an explanatory, mildly argumentative thesis that enables the writer to express an opinion. We infer from the use of the word convincing that the writer will judge the various reasons for protecting the rights of AIDS patients; and, we can reasonably assume, the writer himself believes in protecting these rights. Note the contrast between this second thesis and the first one, where the writer committed himself to no involvement in the debate whatsoever. Still, the present thesis is not as ambitious as the third one, whose writer implicitly accepted the general argument for safeguarding rights (an acceptance he would need to justify) and then took the additional step of evaluating the merits of those arguments in relation to each other. (Recall that Anthony Jones's plan was the "most sensible.")