But according to this argument of “who says its blood is redder,” then keeping a dog or cat should also be a problem, since their diet is meat-based, no?

No, because that isn’t live food. Though of course it should be raised in a non-cruel way, just as with humans.

Even if the food isn’t alive, the original argument still stands: who says the blood of the chicken or pig used as food for the dog or cat is less red than the blood of the dog or cat? And if you’ll say that in fact there’s no preference and it’s done only for the sake of the human who owns the dog or cat, you could make the same argument about the snake.

No, because when I wrote “blood” I meant suffering. There is no value to animal life. It is forbidden to cause them suffering.

Is it really that dichotomous? Animal life has no value at all, and only human life does? Isn’t it just a hierarchy of importance, nothing more? I just can’t quite “see” that they have no value whatsoever.

Indeed, it has no value. I mean that they are not moral entities with rights. We do have an obligation not to harm them. In my view, it’s binary.