Is he grumpy about other issues or just the cats? I find my DH is quite good with our cats, until he gets in a mood, then he grumps about them. When I met him he had a cat and was great with her, so I know that in general he likes cats, he just has grumpy bum tendencies.

It may be worth determining whether is it 100% the cats or if he is just using them to vent his frustrations about other things.