Because I was thinking mainly of idioms in this kind of context. Many idioms wouldn't be said in this context. Other idioms that have even more negative potential include but are not limited to...

"Spare the rod, spoil the child."

"One bad apple ruins the whole bunch."

"Fight fire with fire." (why the Hell would someone fight fire with fire)

"Flies are attracted more by honey than vinegar."

"Tell me who your friends are and I'll tell you who you are."

The idiom in question is "where there's smoke there's fire" and it alludes to the idea that "much ado" is never about nothing, that commotion is never born in a vacuum. This is neither true literally or figuratively (people do not operate in the same way as smoke and fire, people seem more analogous to snow avalanching down a mountain if we are to update the idiom), but the fact it's not even true literally spells out a glaring problem with even invoking the idiom. The reverse statement, "where there's fire there's smoke", isn't true either.