Let's try again. You ask if it should be illegal or not to smoke around children in homes:
For example should it, in your opinion, be legal or illegal to smoke in the home when this results in children being subjected to passive smoke?
When Taz answers with "common sense", I read that as it should be common sense that such activities should be illegal. What else would the "common sense" refer to?
Let's look closely at what he wrote above this answer. He says that having sex in the home is clearly quite okay, that it is legal to do. Having sex in front of children is (or at least, should be; I'm not familiar with chicago/Ill law) illegal. This entire answer he calls "common sense".
He then answers your question about smoking in the home around kids with "common sense", thus suggesting a link between his first and second answer. He even suggests such a link with the phrase "catch my drift?"
I'm fairly positive that Taz thinks this. However, since I can't actually read his mind, I qualified the statement.
I don't see the contradiction you do.