With that logic, the fact that two of my gay coworkers are big dog lovers and one is into raising rottweilers would indicate that lovers of big dogs are gay regardless of what they call themselves.
I don’t think the problem is with him being a cat owner, I think it’s with declaring the cat his “primary relationship”. That might not be gay but it’s definitely weird. I’ve lived my life in a pet world, dogs, cats, a bird, rodents, I understand the pet bond. But at no point has my “primary relationship” ever been with a non-human.