I'm aware of cruel methods used in animal training of all kind. That is totally unacceptable, no matter how "dumb" or "clever" the species. I do wonder, though, why couldn't something like painting, or whatever, be tought to them with acceptable methods.
Elephants are intelligent animals. Why wouldn't they enjoy "brain training" the same way dogs, dolphins and apes do? I can't see anything wrong in guiding the painting by squeezing the ear. I'm not saying the info in the link above is false in anyway, but I don't allow myself to jump to conclusions too fast. And phrases like " It's a myth that elephants are talented, because they can paint" or "circus tricks are degrading and cause mental trauma" are so naive that they throw a shadow on the credibility of the whole site.
There was nothing in the slide show about painting that worried me, but the life of, say, the trekking elephants, isn't nice to watch. It's like the life of working horses in western world 100+odds years ago. Another question, then, is how many "failing" painters, that never get to perform, are treated with heavy hands during the process.
Also, wouldn't a stressed, mistreated elephant be a very risky animal walking around among tourists in groups (like in the video, you see many unchained ones). "Tame" elephants do attack at people all the time. An animal doing something that it doesn't do in the wild does not
automatically mean the animal is suffering or mistreated.
(Wild elephants do make marks in the sand with their trunks, AFAIK)