Company president: Grievance procedures should allow the grievant and

this is a LSAT question, so the argument structure itself is quite complex.
Even though the question concerns with an issue in business, the question is still quite far from a normal gmat question.
Only A and C makes sense here, but the logic in C is still hard to comprehend.
I do not think this question is good for practicing.

Company president: Grievance procedures should allow the grievant and the respondent to select a mediator who will attempt to work out a resolution. Grievances are costly and mediation could help to resolve many of them. However, beginning mediation fairly late in the process, as our human resources department proposes, wouldbe relatively ineffective.
Which one of the following, if true, most helps to justify the company president’s criticism of the human resources department’s proposal?

(A) People who file grievances are unreasonable and would resist listening to a mediator. -weakener
(B) Many disagreements are already being solved without the intervention of a mediator. -weakener
(C) Adversaries’ positions tend to harden as a dispute wears on, making compromise less likely. -Correct
(D) Respondents tend to be supervisors who cannot give in to employees without losing authority. -out of scope
(E) The mediation process itself is likely to cost as much in time and money as the present grievance procedures. -out of scope

Company president: Grievance procedures should allow the grievant and the respondent to select a mediator who will attempt to work out a resolution. Grievances are costly and mediation could help to resolve many of them. However, beginning mediation fairly late in the process, as our human resources department proposes, wouldbe relatively ineffective.
Which one of the following, if true, most helps to justify the company president’s criticism of the human resources department’s proposal?

(A) People who file grievances are unreasonable and would resist listening to a mediator. - WRONG. Weakens overall argument.
(B) Many disagreements are already being solved without the intervention of a mediator. - WRONG. Weakens the overall argument itself. Like A only.
(C) Adversaries’ positions tend to harden as a dispute wears on, making compromise less likely. - CORRECT. If late then mediation also remains most likely ineffective.
(D) Respondents tend to be supervisors who cannot give in to employees without losing authority. - WRONG. Irrelevant. Mediation aspect not touched at all.
(E) The mediation process itself is likely to cost as much in time and money as the present grievance procedures. - WRONG. Cost is out of scope.

Answer C.