When one boos there is certainly the possibility (or perhaps likelihood) that the reason for booing could be misinterpreted by someone. At the same time, when someone says that they booed for "X" purpose, even if you don't believe it, of course that's why they booed. There is distinction between intent and result.
Yeah, but the intent is meaningless at the end of the day. Laviano felt (and reacted) as though he was being booed... and he wasn't wrong to feel that way. Whether or not someone was booing his return, Flood's decision to hold Rettig off the field, Flood's decision to risk Laviano's health, the color of our uniforms, or the font on the program, is irrelevant.
Laviano came out on the field, and people booed... and once the boo was out of their mouths, they have no control over how people (in this case, Laviano) interpret and respond to it.
If you drive past a group of people on the street and yell "F--- you!" out the window, how are they supposed to interpret that? Your intent may have have been to target all of them, one of them, or even the poster of a political candidate on the wall behind them... but intent is divorced from the actual action.
Boos can't be targeted. They're not addressed to anyone, so intent is meaningless. The only thing people hearing a boo have to go by is their own assumptions in the moment, and the booer has no control over that.