I have had people post defensively about things that other people have posted on my wall. It really, really irritates me. It feels like the commenter is trying to start an argument.
A friend, Alice, posted an article about Polka Dot Issue on my wall. The article was pro-Polka, and Alice posted it to my wall knowing that I am also pro-Polka. Betty, Candice, and Donna all liked the article. Eleanor was the first to comment, and it was a very anti-Polka comment. Knowing that I am pro-Polka (as are the majority of my friends), this irritated me. Although Eleanor was welcome to read the article and have her opinion, by posting her opinion on my wall, I felt as though she were taking advantage of the situation.
I use this example because Polka Dots are a huge hot-button topic and polarizes people on one side or the other. It invariably creates arguments. Many people on both sides of the issue find the views of the other side to be offensive. However, using a post on someone's wall as a jump off point to express your opinion on a matter can be extremely rude - even when you really, truly, absolutely believe that Polka Dots or No Polka Dots is a safety issue and therefore not subject to a normal mannerly exchange (and believe me, Polkas and Anti-Polkas both believe their side is the safe one).
I vote for saying nothing. Talk to your friend about the article in person, but do not use her wall to potentially start an argument with her husband. This will put your friend in a very difficult and unfair position and could create tension - either between her and her husband, her and you, or you and her husband - or any combination of these.