Hi ameliakate!
This is an excellent question to ask, as this concept shows up in quite a few Method of Reasoning questions across the history of the exam. It boils down to the difference between attacking a conclusion versus the reasoning behind an argument.
For example, let's say that I want you to believe the following conclusion, in honor of the Academy Awards happening tonight:
Green Book is an incredible movie.
Now, I personally agree with this statement, and as it just won Best Picture, it's a totally reasonable claim. However, quality of the film aside, what if this was the reasoning used in the argument:
Green Book is an incredible movie, evidenced by the cutting edge digital effects used during the fight scenes between the giant robots and the talking gorillas.
Now, here is where I have an issue with the reasoning of this argument. There are zero giant robots or talking gorillas in the film, so this is obviously terrible reasoning. However, as much as I hate the argument, I can do so while still agreeing with the conclusion. It is an incredible movie, just not for that reason.
This process is really common in MOR questions. A second speaker can dispute the reasoning offered by the first, but can do so while undermining the connection between the premise and the conclusion without directly attacking the conclusion.
The conclusion offered by Lopez was that the university was not committed to liberal arts. That idea wasn't attacked by Warrington, who instead questioned the concept that closing the classics department equates to no longer studying classical antiquity. Maybe Warrington is a staunch defender of the university's commitment to the liberal arts, or he/she could even completely agree that the university lacks such commitment, but believes so for completely different reasons.
To further clarify one last point, in your post you mentioned that "Warrington's argument discredits Lopez's conclusion." I would say that Warrington clearly discredited the connection between Lopez's premise and conclusion. They attack the reasoning and leave Lopez with a currently unsupported conclusion, but not one that was proven false or even 'directly attacked.'
I hope that helps, be on the lookout for this situation to show up again!
And, go see Green Book
