I don't consider myself an extremist, and frankly, the more i learn, experiment, understand, how the human body works, what is harmful, what is beneficial, i wonder how so many humans can inhale/ingest so many harmful substances chronicly, willingly, and not care about the consequences.
If you consider that your body is only thing you have to exist and live in this world, then keeping it in a good state must be a priority.
Following this reasoning, the habits of people living with "normal" habits can be considered extreme, because they will destroy, not preserve and build life.
The reality is that once one has damaged his body too much, existence becomes full of pain instead of full of pleasures. Some lie to themselves by interpretating things positively, but it does not change the reality, only their perceptions.
Taking care of one body is a necessity if one wants to live long in a functional body and enjoy his existence, pain, discomfort, are distractions, they are not welcome.
I agree with you that some are a bit extreme with their strict diets or cleansing procedures, and i don't recommend to become extremist, but i certainly recommend periodic cleansing, smart nutrition, moving the body regularly, enough sleep, enough exposition to the sun, clear goals, constructive thinking, work, uplifting relationships, peace.
Eat your chocolate and enjoy it, but not everyday, only for the pleasure of the senses, not for life.