The apple doesn't fall far from the tree in terms of how James Harlowe, Esq., and Junior treat Clarissa. While he's not the worst dude in the world, it's not a great idea to get on Daddy Harlowe's bad side. Not only does he refuse to forgive his daughter for running away with Lovelace, he places a curse on with her that will follow her to the afterlife. That's intense.
Plus, he doesn't have the most direct communication style. When Clarissa is left alone with him, she observes that he "looked so very sternly that my heart failed me, as twice or thrice I would have addressed myself to him; nothing but solemn silence on all hands having passed before" (9.34). And when he finally does speak, it's in an "angry monosyllable" (9.36). We're just guessing here, but Daddy Harlowe seems like a prime candidate for family therapy.
We've got to admit, though, that Dad is sometimes right. He shouldn't be trying to marry his daughter to old Solmes, sure. And the curse thing is a little over the top. But Lovelace is bad news, and we heard it from the big guy first. Maybe he has some control issues, but it also seems like he's genuinely worried about his daughter.