Members of the Philadelphia-based back-to-nature group called MOVE seem to have gone crazy some years ago. The Philadelphia authorities joined them Monday. That was the day they bombed West Philly, destroying a mostly black middle- class neighborhood in order to save it from the five adults and 12 children known to be holed up there. It is possible, though hard to imagine, that subsequent developments could justify the bombing that destroyed scores of houses and jeopardized who knows how many lives. But the immediate official explanations defied rationality. "I don't know at this point . . . however the chances of the fire having been started by police is better than 50-50," Mayor Wilson Goode said, while crediting the officers with "tremendous restraint." He accepted responsibility for the bombing, adding that it wouldn't have been carried out if it had been known that the resulting fire would destroy the neighborhood. "We believe we did what we thought was appropriate for the occasion," added Leo A. Brooks, the former Army general who coordinated the siege. Both Goode and Brooks are black, a fact that may provide them some protection in the wake of Monday's insanity. If Frank Rizzo had been either chief of police or mayor (he formerly held both posts), America -- and particularly black America -- would have been outraged. They still ought to be. It's easy enough to grant that the authorities didn't intend to burn down an entire neighborhood to rout a handful of armed crazies. But even so, their actions seem excessive. The intention, they say, was to drop a "percussion" bomb onto a rooftop bunker in order to blow open a hole for a tear-gas assault. But percussion bombs, according to some who claim to know, don't make fires, leading to speculation that the device dropped from the helicopter may have been an incendiary bomb. In any case, the officers acknowledge that they decided not to extinguish the rooftop fire, in hope that it would destroy the log-reinforced bunker there. "Minutes after the bomb exploded, smoke poured from the house," the Associated Press reported. "The fire spread to nearby houses, and authorities let it burn almost 90 minutes before turning on water cannon and calling in fire trucks." The fire chief said his men were unable to approach the MOVE house because of sniper fire. Nobody blames the police for carrying out their court-ordered eviction of the well-armed and defiant MOVE members who, according to neighbors were living in incredible filth and who used powerful loudspeakers to threaten neighborhood residents. Nobody blames the authorities for returning the fire of MOVE members who fired at them. Even the bombing might have been explainable if it had come in some desperate attempt to save lives that were in immediate jeopardy. But the neighborhood had been evacuated already, and the bombing followed a lull of several hours during which no shots were fired. You'll find no apology here for the fanatical followers of a third-grade drop- out who menaced neighbors, eschewed soap and water, kept scores of dogs on their premises, welcomed rats as "a part of nature" and defied court orders to vacate their filth-filled rowhouse. But what was wrong with a combination of tear gas, water cannon and the patience to wait them out? In their resort to airborne explosives, whether incendiary or percussive, Mayor Goode, Managing Director Brooks and their minions bombed out.