Well yes, "onmicause" was coined for a specific bundle of left wing beliefs, but the phenomenon exists on both sides.
I am trying to think of equivalent terms the the left use to label the same phenomenon on the right, but the only ones I can think of are "fascist" and "Nazi" which are mostly now used outside their original meanings to label a general bundle of assumed rw beliefs.
I think it's because as PPs have alluded to, within the onmicause these vews are seen as the only moral positions to hold, so while the right(ish) and the outside-the-omnicause left have given the onmicausers a gently mocking label, those who oppose any part of the onmicause are cast as morally bad people.
I am broadly centre left myself so it's not like I'm trying to avoid an obvious term, I just can't think of any.
"Hard right" is the closest non-attacking equivalent that springs to mind right now. Or in the US, MAGA.
Or not exactly right wing, but "Centrist Dad" would be a similar belief bundle label. Actually that makes sense, in that the Centrist Dad is left leaning enough to escape the moral censure so he gets a gently mocking label.
Although I do understand why it might sometimes be useful to ask, “but do you really think that, or are you assuming it’s the right opinion because it’s what the people who think like you on other issues think?”
It would be incredibly useful to ask, but realistically no one in the heat of a political disagreement is going to consider they may not be thinking their own thoughts. That's a question for a close friend or therapist to ask very carefully outside any active debate.