Otis: Aristotle's principle of justice says that we should treat relevantly similar cases similarly.
Otis's 1st Claim:
Aristotle's principle of justice says that we should treat relevantly similar cases similarly.
Does Tyra dispute this? No. She explicitly accepts it.
Otis's 2nd Claim:
Therefore, it is wrong for a dentist to schedule an after-hours appointment to suit a family friend but refuse to do it for anyone else.
Does Tyra dispute this? Yes. She explicitly says "it's not unjust for dentists to do that."
Evaluate
In addition to accepting Aristotle's principle and disputing Otis's conclusion about dentists, Tyra offers a particular type of pushback: she defines / distinguishes something Otis has said. This is a common Rebuttal archetype and it shows up frequently on 2-Speaker Method questions.
When Otis applies Aristotle's principle to the Dentist situation, he's assuming the situation triggers the principle: that the situation of a friend and a non-friend are relevantly similar, and should therefore be treated similarly. Tyra distinguishes friends from non-friends, showing them to be meaninfully different. It is on these grounds that she disputs Otis's conclusion: she implies that Aristotle's principle isn't applicable to this case.
Goal
Look for an answer that says they disagree about Otis's conclusion, or his assumption that Aristotle's principle should apply in this case.