The subject is a bit of a sore spot for me and, I suspect, many others. I can’t count how many times, in yeshiva, I was mocked and imitated for my pronunciation of the cholam as “oh.” Something so simple and so clearly stated in dikduk has become a pivotal point by which a person’s level of frumkeit is assessed.
The “oy” is a comparatively recent phenomenon, born out of the Eastern European dialects of Yiddish. Anyone with a clear grasp of linguistics (not stressed in many yeshivos) or history (not stressed in many yeshivos) would be able to confirm this. Yet, many of those same bachurim who were so stringent on chalav yisrael that they would refuse to eat at the table with someone eating chalav stam never took the time to examine the rules governing the words they recited every day.
It takes a special level of shallowness for a ben Torah to treat the entire beis midrash to an Oscar-winning performance of his krias shema–complete with moving the head in four directions, scrunching up the face as though being tortured and doing things with the “ayin” that would send anyone knowledgeable in dikduk diving for cover–and then turn around and mock his fellow for saying “oh” instead of “oy.”