Calling it a special consideration for big business, Consumers Union and the California Rural Legal Assistance are recruiting opposition to a $6.2-million bill that would compensate growers, retailers and others for losses suffered when the state ordered the destruction of aldicarb-tainted watermelons last July. The measure by Assemblyman Norm Waters (D-Plymouth) is expected to be voted on by the Assembly next week. Assemblyman Lloyd G. Connelly (D-Sacramento) told reporters that "we don't do this for anyone else in the state. If the dam is about ready to break and we have to let the water out and the people along the edge of the river are flooded . . . we don't provide compensation."