Slapping him doesn't mean he had anything to do with the shooting. A lot of people wanted to "slap" Colombo at the time, just that Carlo IF we were to believe the son was like a father figure to Colombo sr, was the only one that could

Not to mention, if Carlo wanted Colombo dead he would have got him whacked inside that bar. NOT in front of the worlds media and woman/ children (Gambino is gonna trust a black guy not to accidentally shoot any innocents??)

That had the hail marks of political assassination written all over (the son seems to think that too)