"Every single posture in every single Bikram Yoga class
is modified at every single moment."
This is not something that suits everyone. Especially if you have prior training which has 'set' your body up in a certain way, or you've picked up bad habits, or if you just plain don't want to; change within ourselves if often the hardest battle of all. However, Bikram Yoga is this way because it's therapeutic, and because it means it's safe, and that means it's for ANY body, shape, size, age and so forth.
There's a million things someone can do with a fit and healthy body, but only so much one can do with a broken body - and this style of yoga is one of them. It makes people change their perspective, learn patience and relearn everything, so sometimes the ego might get a bit bruised, but isn't that a good thing?