Trotsky's comment that Stalinism differed from fascism -- even German fascism -- "only in its more unbridled savagery" came before the implementation of the Final Solution. By that point I think the "more unbridled" idea lost its truth.
Secondly, slavery in the USSR. This was certainly true in the 1930s. But far less so in later decades. For most of the years of the USSR's existence the relationship of the worker to the Soviet firm was analogous to the serf industrial production of 18th century Russia. Russian workers were "state serfs," not usually slaves (and not wage-workers selling their labor power, either, as "state capitalist" theorists would have it).
Thirdly, while Joseph Carter's theory of bureaucratic collectivism led heterodox Trotskyists to abandon the economism of the orthodox, and to abandon the illusion that the USSR was a "strategic gain" for the global working class, it should be obvious by now that the Stalinist societies did NOT represent a new mode of production which might supplant capitalism and that the ruling elites of these societies were not a "new class." The collapse of the USSR and Eastern European Stalinism discredited ALL of the theories that emerged from the Trotskyist groups (degenerated/deformed workers' states, state capitalism, bureaucratic collectivism).
Was Stalinism -- or at least "late Stalinism" -- more reactionary than capitalism? In some ways yes -- because while capitalism "automatically" leads workers to form unions and political associations, even clandestine ones, Stalinism completely atomizes its workers (which is why socialist revolutions in such societies was never a real possibility). But there were certain material gains for workers in the USSR and Eastern Europe (and China) that have been completely lost in those societies' transitions to capitalism (particularly in Russia, where the transition resulted in utter chaos, a decline in the total population, etc.).
I think the Third Camp position was broadly correct but we should recognize all of these realities.