Independent of all else, in this decade, in this country, the words “Fuck you!” are not by themself sufficient incentive to get anybody punched. As verbal assaults go that’s positively milquetoast.
Of course the equation changes if the criminal was looking for an excuse to punch people, for reasons entirely independent of being offended. In which case the “Fuck you” wasn’t taken as an insult and didn’t offend anybody - it merely served to highlight the speaker as a target.
Which is to say, as every english-speaking person knows, yelling “fuck you” isn’t enough to get you punched. It’s simply not offense enough for a person to even pretend it’s causative - not credibly, anyway.