Because he wanted the wildlings to think Jon was a traitor to the Night's Watch so he could infiltrate their camp. Jon kills him to prove that he is no longer loyal to the Night's Watch in the hopes that the wildlings will believe his betrayal and take him in and he can become a spy.
They explain it so much better in the books
What's the exact threat that the Wildlings pose anyway? They just seem like a bunch of nomads with weapons.
Season 1 > Season 2. Gratuitous female nudity is beyond ridiculous. So transparent and so annoying
Final episode was OK. I guess if you've read the books you can't help but be underwhelmed. Only Arya , Tyrion and Stannis stood out his season. I'm a huge fan of Danny's but her season 2 was average at best. Love the dragons though...
I thought the nudity was way more gratuitous in season 1. Agree re. Dany though. I'm glad she finally did something in the last episode after spending the whole season whining and posturing and being annoying.