Why does it say "Hoy Moshchei he'Avon b'Chavlei ha'Shav."?
Brachos 24b: This refers to one who walks in a filthy alley, and continues saying Keri'as Shma.
Rashi (from Sukah 52a): They incite the Yetzer ha'Ra on them a drop at a time. Initially it is "Chavlei ha'Shav" - like a thread of a spider web. After the Yetzer ha'Ra incited them, it gets stronger, until it becomes like ropes tied to a wagon via which it is pulled.
Radak: Just like one who pulls a loaded wagon via ropes, so they pull sin to themselves forcefully. Their ropes are of Sheker. The sin is pleasure, drinking wine, which draw a person to Giluy Arayos, theft and murder. They draw the Aveirah on themselves through accustoming themselves to pleasures and drinking wine. And so Shlomo said - "Limshoch ba'Yayin Es Besari" (Koheles 2:3).
Malbim: When a person encounters something pleasurable that is forbidden to him, he has an inner war. Desire arouses him to benefit from it. Intellect warns him not to touch it, due to Hashem's Mitzvah. When desire overpowers and he transgresses, this is called Chet in Tanach. He deviated from the goal and transgressed; he is guilty. Such sinners are full of regret. After they fulfill their desire, they open their eyes and recognize their evil. Some people, in such an inner war, use the intellect to help desire. They deny the Mitzvah or the Commander, or reward and punishment. This is called Avon; he intentionally made his way crooked. He will never regret. The Navi argues with such people here "ha'Omerim Yemaher Yachishah Ma'asehu" (19). They deny Hashem's punishments. [The Navi] charges them to investigate the primary reason that caused them to cast off the yoke, if this was due to intellectual investigation. Really, it was desire for forbidden matters.
Why does it say "uch'Avos"?
Radak: The Chaf is of comparison. Just like they draw a wagon via ropes, so they draw sin on themselves. Avos is a three stranded rope.
What is "Shav"?
Rashi: It is something without substance.
Malbim (18-19): They are not thick ropes [that led them to deny Mitzvos, or reward and punishment. They are ropes without substance. They drew sin on themselves via intellectual claims, that Hashem's acts and counsel are hidden, since they do not come immediately. This is an empty claim. Hashem delays punishment to allow room for choice, or to do Teshuvah, and the known reasons!
