Mark 7:1-23 has a lot in it that I could talk about, and I hope to get around to it at some point in my Mark Tidbits series, which I have not abandoned. I have a partially-written fourth post in that series that I keep moving forward because I haven't had the time to finish it when I haven't had something else higher on my priority list at the time.
Jesus' argument in this passages is in two stages, with a third implicit step. His opponents accuse his disciples of not following the traditions of the elders. He makes two points in response.
First, he directs a comment to the scribes and Pharisees who have taken it upon themselves to show him how much of a lawbreaker he is. His response is basically that they are in violation of the Torah themselves. They use a Torah command to keep vows to God as an excuse not to keep the Torah command to honor their parents. They vow enough of their possessions to God, which means they have to give it to God and not their parents in their parents' old age. Apparently they were able to avail themselves of its use in the meantime. This is not only an inconsistency in their own thinking (by saying they follow the Torah but violating it). It's also a misuse of the Torah passage they used to support the practice.
After pointing out their inconsistency in violating the very Torah they claim to place as the highest priority, Jesus moves on to the real issue. After all, showing that they break the Torah doesn't show that he is ok to do so. So Jesus gives an analogy. Normally, someone giving an analogy will find some other item relevant to the discussion at hand to illuminate the issue. That's not what Jesus does. He takes the issue they're discussing as an analogy in itself for something more fundamental. It's an analogy for the issue not of unclean things going into you but what the Torah was symbolically dealing with in all its cleanness regulations. That more fundamental issue is moral cleanness, which Jesus refers to as what comes out of you. He gives a list of examples to make it clear what he means.
What's most interesting here is that he does a standard logical maneuver, but he does it in a very unusual way. The standard maneuver is to identify a false assumption of the opponent's argument and then to dispute it. His way of doing it is to give the subject at hand as an analogy to something else, ending up turning the discussion on its head and denying that the action in question is important in itslef without reference to more fundamental issues.
I think there's a third component to the argument, which is implicit, but when you put together the first two points, the third point seems hidden beneath the surface. He has shown that the tradition they've developed contradicts the Torah in at least one place. He's also disputed that the real point of the Torah is even about what its surface application was about. I think the implicit conclusion we're supposed to draw is that, if even the Torah isn't fundamentally about what it seems at the surface to be about, then a fortiori the traditions of the elders, which he's shown to go beyond the Torah, do not bind his disciples. QED.