He was perversely slow to——
He is too stupid to make a blunder
As impassive as a statue
He is inflexible to all entreaty
He has been inexorable to all invitations
The victim of his own prejudices
The dupe of his own stupidity
Empty of the kernel of good sense
He made a plump refusal
It is like trying to use a large screw-driver to turn a small screw