The day my daughter and future son in law told me that the planned to get married, I congratulated them and told him that if he ever hurts my little girl, I'll kill him. He knows that I meant it.
I love him like a son, he's a great husband to my daughter and a wonderful father to my grandson. He's a great guy. I just wanted to establish a base line that couldn't be crossed.
You sound exactly like my father. He's said the same to the three guys who married my three sisters. He is a jovial, peaceful man. Far and away more peaceful than I.
But when he talks in full sincerity, no one doubts him. And I don't doubt you.