A child was shot in a Dorchester park Monday night, and motorized dirt bikes emerged as the villain, with the city moving swiftly to ban the buzzing vehicles, which the mayor and police commissioner blamed for fostering mayhem.

City officials acknowledged yesterday that their assertion is based on anecdotal evidence, mainly citizen complaints, because they do not keep statistics that indicate the bikes are used to commit crimes. And now, some community members, and at least one city councilor, say the crackdown, dubbed Operation Kick Stand, is a knee-jerk reaction that distracts from the underlying issues that lead to street violence.

“We have so many people who are leading very desperate lives in our society, and some are resorting to taking out their frustrations by opening fire on a local playground,’’ Councilor Charles C. Yancey said. “That should certainly deserve as much attention by the local administration and the media as these bikes.’’