Somebody becomes a ben sorer u'moreh (wayward and rebellious son) if they steal and take that money to buy meat and wine. It depends on the context: how they stole it, where they stole it from, where they ate the meat and wine, where all that went down. That affects whether somebody is going to be considered a ben sorer u'moreh. The Mishnah says, if he stole money from his father and then bought meat and wine with it, and then ate it also on his father's property; or another case, if he stole money from other people and bought meat and wine with it, and ate that meat and wine on some other property; or, or he stole money from others, bought meat and wine, and consumed that meat and wine on his father's property. In all of these cases, unless he steals from his father, buys meat and wine with that money, and then eats the meat and drinks the wine on the property of somebody else.
What we're really saying here is that they're putting this kid to death because he's going down a very bad track in life, one of pleasure, of self-indulgence, and he's going to just continue down that road and eventually get to a point where he murders to support his habit. So what we're saying here in this Mishnah is that to be a ben sorer u'moreh, it has to be done a certain way: you first steal from your father. If you steal from your father, that's the easiest way to get it done. A person is in his father's house; he's around, he's always there, so that's the easiest way for him to do it, as opposed to stealing from others, where it's more difficult and he may not continue down that difficult path. But he's going to the easy path of stealing from his father, and then even the eating has to be done on somebody else's property.
If it's being done on somebody else's property, he doesn't have that fear of his father catching him. So that's also easier—to eat elsewhere, away from his father, where his father doesn't see that he's drinking the wine and eating the meat. That's considered to be an easier situation, where he doesn't have that fear within him. So that's how he becomes a ben sorer u'moreh: he steals from his father, buys meat, and then eats that meat and drinks that wine on a different property. Not only does he have to steal from his father in order to be a ben sorer u'moreh, but, as we learn from the actual pasuk (verse), it says that he violated both his mother and his father. So this opinion says that it can't be that he just stole from his father; he has to steal from his mother as well.