ASOIAF: Why does Ned Stark act so pious about Jaime and Cersei's treason when he committed treason by sheltering Jon Snow?

There are worse crimes than treason. Letting your friend murder your baby nephew is one of them.

Now, not telling Robert about Jon was treason, arguably. Though if everybodythinks that he is Ned’s son, including Jon himself…and if nobody else really knows he is actually Rhaegar’s son….

Where is the harm?

For all practical purposes, barring some, I don’t know, unforeseen event where Jon’s crippled brother/cousin Bran sees the past through a magical network of weirwood trees — which Ned has no idea exists — it really is no harm to Robert himself. And Ned preserves a baby’s life. Who is also a kin. And there is no crime greater than kinslaying in Westeros.

In fact, by telling Cersei Ned also acted to preserve Joffrey, Myrcella, and Tommen’s life too: because make no mistake: Robert would have killed them too.

Ned acts consistently. He is not a traitor at heart. He moved to keep Jon alive and make sure nobody (except for that guy in the swamps) knew about it: Jon packs off to the Wall, swears an oath of celebacy. No one is harmed. Bob is Ned’s uncle.

Written Feb 10