A young group, ideologically committed to capitalism and opposed to taxation as a form of "slavery," picketed the State House from 10 to 11:30 yesterday morning. The 30 pickets of the New Right Coalition garnered lots of attention from tourists, but not Gov. Sargent whom they criticize for insistence on new tax money. Sargent, described on one picket's placard as "Massachusetts answer to George III," is not at the State House on Saturday.