Racial attacks like the ones behind the arrest of 32 suspects in Denver are part of a trend spreading across the country, gang experts said Saturday. As part of the trend, black gang members videotape the assaults in trendy tourist districts and sell them on the underground market as entertainment. "They knock a young white guy out with one blow to see if his knees will wobble and surround them and take their money," said the Rev. Leon Kelly, who runs a Denver gang-prevention program. "It's a joke." The gang members crave the notoriety of having their one-punch knockouts recorded...