when I told you to hunt him down and kill him, you couldn't find him. That's what it means
For 300 years we kissed Tully boots, swore oaths to them and their stinking fish banners. Not again. Riverrun is ours
If I have the sense the Gods gave a fish, I'd hand you both over to the Lannisters
Riverrun belonged to House Tully for a thousand years. Now it's mine