Whenever there's a mishnaic statement that includes R. Yehudah's opinion, and it I closed the wording of "aimatai," he's clarifying not arguing -- when does that apply? The Gemara's case is the populations that are disqualified from giving testimony - all gambling categories, and people who mess around with other people's money, which suggest the person is not trustworthy. The Gemara qualifies that though - if the person is gambling for fun, and not as his or her income, then there's room to say such a person is kosher to testify. But is this a clarification or a dispute? Alternatively, the handling of the money may be less problematic than the initial sense of gambling. Note the formula information as to how mishnayot work - including using parallel cases. Also: 8th perek - from the mishnah: How do people join together for an eruv techumin? A barrel of food, stipulated for use by all - as long as they too sign on (with intent) during the day. Which brings us to the case of a 6-year-old who needs his mother, who is included in his mother's eruv. But what does it mean to need or not need one's mother?! And why the age of 6? A comparable case from the mitzvah of sukkah... The case can be turned around to focus on the one who does not need his or her mother (parents) - which is the more exceptional case, as compared to the age per se. In the end, the Gemara refines the case to have far more complicated parameters, as to why the child would be included in the mother's eruv. Plus: How much food for the eruv, and what kind of food? Note that the Gemara acknowledges the dessert of Shabbat.