I love cats quite a bit; in fact, currently the only 2 beings in my hometown whom I can comfortably cuddle with are cats: my aunt's cat at home, and a tabby cat that's often walking around in the neighbourhood.
However, I do think it's probably a false assumption to say that ALL autistics have a preference for cats, as a couple of posts above point out. It's a generalisation.
I attribute my relative ease at getting along with cats to their general manner of approaching their environment: cats tend to be very cautious, assessing the situation from a distance before they do anything- whether enter a new territory, stalk a prey, or make contact with a fellow cat. They like finding themselves at higher ground, so that they have a vantage point; if tree branches aren't available, they'll sit on stairs, balconies, high upon furniture, etc.
At the same time, the way cats do interact with each other doesn't necessarily appeal to me. Being mostly solitary animals, whenever they do engage (for example to mate, or to have a territorial conflict) they are not particularly friendly. The exception are usually cats who have grown up together in the same family, or stray cats that form packs in and near human settlements such as urban areas.
I think the reason I can often get along well with cats, is that both for the cat as well as me, the social rules of our respective species no longer apply. We just relate to each other as 2 living beings, without human language or cat language. This removes social tension significantly.
Whereas dogs (who are far more immersed in hierarchy and social structures) usually approach human beings from the perspective of dogs, with all the social rules that come with it. A dog approaches you and expects you to be speaking your language; a cat may or may not approach you, yet doesn't force its social code upon you.
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clarity of thought before rashness of action