You forget that the Starks were leaders of a rebellion that killed her entire family except her brother and an elderly granduncle.
Danny doesn't know the history that well (and the difference between Starks and Lannisters), but Lannisters are to blame for that. When Starks arrived in KingsLanding, Jaime had killed the king, Lannisters have sacked the city and killed the remaining Targaryans.
Ned together with Robert leaded the rebellion, but wasn't to blame about the massacres in KingsLanding.