HaLeivi > no person in Tanach or Torah Shel Bal Peh criticizes Gedolim of previous generations. S
I agree that we need to show respect to all (acceptable) opinions in the past. The current machloket is on what is “acceptable”. Gemora filtered out those that were not. We are not counting various sects mentioned on Gemora as viable opinions. An extremist view (both on the left and on the right) is only to count your own group as acceptable. A more expansive view is to count anyone who is a great Talmid Chacham as acceptable as long as he affirms halakha (Acher was a learned person, but rejected halakha openly, as do many academics or reformim).
Another question is – where is boundary between generations. Sometimes it is imply teacher-student (R Akiva wins against chaverav, but not against his teacher), but more generally we have longer divisions – tannaim/amoraim/rishonim and there are arguments within them. When did the previous era ended? Maybe with Shoah and move to US and EY? Or with Mishna Berurah?