I unintentionally made a bunch of people very angry when I commented elsewhere that either of my dogs is more a "person" than an embryo is. On reflection it was kind of predictable, but to me personhood has nothing to do with abortion laws so it didn't immediately register that I was about to get whacked with a 'pro-life' hammer. I'm just really impressed by my dogs f(^_^; I wondered afterwards if some of the ire directed toward me was caused by the negative use of dogs in English: "I wouldn't treat a dog like that/ treated worse than a dog/ not fit for a dog."
We have many dog-related idioms, most of which don't give dogs a great deal of respect: bitch fight, work like a dog, dog's life, in the dog house, treated like a dog, every dog has his day, sick as a dog, hair of the dog, dog tired, dog eat dog, dog's breakfast, fight like cats and dogs, raining cats and dogs, see a man about a dog, wag the dog, the dog days of summer, let sleeping dogs lie, dog day afternoon, like a dog with its tail between its legs, and like a dog with a bone.
In Japanese idioms, dogs get a mostly negative treatment as well:
犬も食わない (not even a dog would eat it), 犬と猿/犬猿の仲 (dogs and monkeys, basically the same as cats and dogs in English), 負け犬 (a looser), 犬死する (die in vein), and 犬も歩けば棒に当たる (similar to every dog has his day but with more of a connotation that good things will come if you take action).
I'd love to hear from speakers of other languages. How do dogs fare in idioms around the world?