The mere fact that the other families sided against the Corleones for the killing of Sol and McCluskey showed their respect for Sol as one of their own.
The novel makes clear that the reason the families lined up against the Corleones was that the cops told all the families that no rackets would be tolerated until the killer of McCluskey was given up. An emissary from the families asked Sonny to give up the killer. When he refused, the war started.
Ntra la porta tua lu sangu � sparsu, E nun me mporta si ce muoru accisu... E s'iddu muoru e vaju mparadisu Si nun ce truovo a ttia, mancu ce trasu.
