I think it is important that people who ask about morphing axolotls are properly informed and not told that it is awful/cruel/ horrible/wrong without detailing why.
Many axolotls have been subjected over the years to attempts to morph them and many of these attempts have been cruel. However a lot has been learned from properly conducted published works.
If appropriate doses of thyroid hormone are given in an appropriate way to a young axolotl about the size a tiger salmander would normally morph they morph into a creature which is robust and usually lives as long as a tiger salamander.
They do not often morph in bad water conditions and attempts to morph them by warming, lowering the water or using iodine are cruel and ineffective.
Hormone treatment applied too early results in tiny salamanders which do not feed well and treatment of sexually mature axolotls results in morphs which seem to drop dead very quickly, so there is some truth in the story it shortens their life.
With regard to the ethics of creating a morphed salamander I see it as less evil than taking a wild bred tiger salamander from a breeding population and shipping it halfway round the world (I believe all the tigers available to me in the UK are of such a type).
The hormones used to produce morphing are not readily available without prescription in most countries. There is someone who appears to be suppying well artificially morphed axolotls into the Australian market.
I have artificially morphed one of my axolotls. It is a healthy creature, now three years old and interesting and different in a big way from my other axies. Early in the morphing proces it ate like mad, then ate nothing for eight weeks before settling down into an easy to care for healthy salamander. It burrows in soil but still also likes to sit below the surface in a shallow bowl of water.
Done right morphing is not cruel, they should not die in the process and they should live years. Despite that my advice is unless you know what you are doing- don't. If your axolotl is already adult I believe that attempting to morph it is cruel and justifies reporting as such to the animal welfare organisations such as (in the UK) the RSPCA.