EXCLUSIVE

Scott Baio's not getting the justice he wanted -- the wife of the Red Hot Chili Peppers' drummer will not be charged for physically attacking him ... and Donald Trump may have played a factor in the decision.

The Ventura County D.A.'s office rejected the case against Chad Smith's wife, Nancy Mack ... they say because the assault just wasn't that bad.

TMZ broke the story ... Scott was at a school event for his daughter when Nancy confronted him over his vigorous support for Trump. Scott says she beat on him and then started berating him, screaming, "Grab 'em by the pussy!!!"