is stated with regard to a case of disqualified witnesses and fit judges, i.e., the litigant claims that both the witnesses and the judges are disqualified and proves his claim only with regard to the witnesses. R' Meir holds that since the witnesses are disqualified the judges are also disqualified, as the litigant’s entire claim is deemed credible. The latter clause, where R' Meir rules that a litigant can disqualify witnesses, is stated with regard to a case of disqualified judges and fit witnesses, i.e., the litigant proves his claim only with regard to the judges. Since the judges are disqualified the witnesses were also disqualified.
Rava objects to this interpretation: Granted, in the former clause, it is reasonable that since the witnesses are disqualified the judges are also disqualified, as, since there is the option of going to another court, disqualifying these specific judges has no irreversible effect on the outcome of the case. But in the latter case, how can R' Meir hold that since the judges are disqualified, the witnesses are also disqualified without proof? This disqualification nullifies the entire case, as there are no more witnesses.
לא צריכא, דאיכא כת אחרת.
The Talmud answers: No, the Mishnah is not referring to a case where there are no other witnesses. The dispute between R' Meir and the Rabbis is necessary only in a case where there is another set of witnesses, which the litigant did not disqualify. Since disqualifying this set will not predetermine the outcome, the litigant’s claim that these witnesses are disqualified is accepted.