That fresh punk, how I love him,"" Casey Stengel would grin. But not everyone feels that way about Billy Martin, who can careen out of control like a wild pitch or detonate like a cherry bomb. Smith takes a nice balanced view of the Yankee spitfire manager with his aptitude for winning on the field but getting fired by the front office. Will it happen again, now that Billy the Kid is back with the Yankees where, everyone agrees, he always belonged? Smith seems to think it probably will, sooner or later--just like in 1957 when the ruffian second baseman was traded away after the famous Copacabana brawl. And, as Smith points out, Billy's a lot more appealing when he's fighting management than when he's bullying some player fallen from favor--like Ken Holtzman or Elliott Maddox. As to where all that fight comes from--well, there's Billy's smallish size, dirt-poor and fatherless childhood, and (probably) deep-seated feelings of inferiority masquerading as brashness. An appealing sports bio--and well-timed, since Billy's hogging the sports pages again with the Yankees pennant drive and the simmering Steinbrenner-Martin feud.