Could you define "owning a character" please? I don't understand how you do it. Is it a fictional character that doesn't exist in reality? Is it a character Simeon's creates for roleplaying and plays it?
If we're talking about a fictional character, then you can't "own" a character. It's just an idea you have. You don't control it, you create it. The ethical difference is that with a robot you can actually control something, even if it's there's no difference between it and your dishwasher.
But, the sex robot usually is not just a machine. They are given personality, they are linked to a character in the owner's mind. They are given life by the owner. And then, owning a sex robot and "owning" a character are both part of the same thing. You said that you can have sex with a character by putting an avatar of yourself in the story. A sex robot could be the opposite thing, putting an avatar of a character in our reality.
I see no difference appart from the physical thing that happens with robots. The article's writer probably overreacts to the fact of men owning something that resembles a living, human woman, specially thinking that the only difference between a sex robot and a vibrator, or some of the more technological sex toys, is complexity. They're both things you own, program and use.