Anybody else get extremely annoyed that people are complaning/ranting about the Loras betrothal(s) because they think he's in the Kingsguard? Its pretty amazing how some bookreaders just can't separate the two entities and continuities. They end up missing a lot.
There has been plenty of context, Karstark himself has voiced disapproval (in season 2): There's also Catelyn reprimanding Robb last season and reminding him that he is breaking his vow with the Frey's.