The fact that you and others, even if there are millions of them, think treating a cooperating uke this way is "normal" makes little difference to me, and does not make it safe or desireable. One of my teachers flatly calls it "unethical" and I agree.
I agree, I call it out-and-out abuse and brutality. I've seen it for many years, in many different Aikido demonstrations and dojo etc. After 25 years of teaching Aikido, I've experienced many different styles and teachers. Abuse perpetrated during the demonstration and teaching of Aikido is rampant, well-known among people who are willing to see it and admit it's existence, and completely unnecessary.
I know it's divisive to say this, because it appears to be a direct attack on either a teacher or a style etc. But there's no way to discuss it openly other than being honest about one's perceptions and experiences. In my experience, a lot of what is called Aikido is simply a demonstration of Aikido techniques, which I've seen a lot of instructors take advantage of to make themselves look powerful etc. In the end, it's the uke who pays, unfortunately, and the many people in Aikido who think they are learning something that they're not necessarily really learning.
I remember talking with Terry Dobson once many years ago, he was saying that he believed that a lot of why he got sick was because of all the hard falls he took all those years at Hombu dojo. He died a while ago.
Of course there are a lot of people who have a different experience. They're lucky.
I have nothing against "hard" Aikido, although it's not my style or preference. But there's a limit to what is acceptable. Nor does "hard" mean effective, in fact often it can defeat it's effectiveness, especially in "real life."