Activism, in a general sense, can be described as involvement in action to bring about change, be it social, political, environmental, or other change. This action is in support of or opposition to one side of a controversial argument.
There are many different forms of activism; a select list follows.
... can have very distressing side effects. Illegitimate treatments, e.g. herbal medicines, do not have these side effects -- they have no effect.
Distrust of conventional ...