Observing from the sidelines... it looks like this suffixation started with 'homophobia.'
At a time when Freud's writings were accepted as received wisdom by many, the idea was that lack of tolerance of homosexuality indicated a latent homosexuality in the aggressively intolerant. The active intolerance was hypothesized to be a psychological protection against seeing something unacceptable in their self. (Sort of an intellectualized 'takes one to know one')
As society became more intolerant of intolerance, the suffix is used for other intolerances despite Freud being less influential. These days it seems more akin to medical jargon that translates things into Latin or Greek to obscure the simplicity of the condition or that medicine has nothing useful to say on the subject (e.g., idiopathic, iatrogenic, atropic).