They are scared of the slippery slope fallacy is really all there is to it for the majority of em. I don’t know if having a logical discussion about it is possible because well…it’s a fallacy. It’s literally illogical.
Slippery slope is a mixed result of fear and lack of trust which are both subjective and highly irrational emotion areas. Trust and Fear are usually our worst offending emotions when it comes to accuracy which is why you are not really supposed to base your argument on them.