Dozens of medical marijuana activists rallied outside Los Angeles City Hall, declaring war on an enemy. Their target was not the federal government, whose agents raided several local dispensaries, or neighborhood groups trying to shut down the city's estimated 700 pot shops. The enemy was fellow medical marijuana advocates. Three competing measures on the May 21 city ballot have divided L.A.'s lucrative medical cannabis industry, with each side accusing the other of trying only to protect profits, not do what is best for patients.