There are many schools of thought with bonsai. Very many people use "clip and grow" techniques. Wiring techniques are more popular in Japan than in China from what I have heard. I'm not that experienced with bonsai, but the people I have talked to are not so keen on the production of artificial "jin" (bleached dead wood). If there are dead parts of your tree, you need to do it to keep the tree healthy. An abundance of jin seems to be more of an American style than Japanese in my limited experience.
In any case, I don't think the treatment that bonsai trees undergo is harmful to them. In fact, they are arguably much healthier and "happier" than a tree that's left to grow. The pruning of the roots makes them incredibly vigorous because they have many more feeding roots for their size than normal. You have to baby these trees too (i.e., water it every day) because the soil can dry out very quickly (there isn't much of it). So inevitably they are free of disease and insect infestations.
If you spend some time around well cared for bonsai it's pretty obvious how healthy they are. I see no evidence at all that the trees suffer. Quite the opposite. I recommend learning more about it if you are interested in the welfare of the trees (something that I won't criticize anyone for).