I recall being an anti-authoritarian teenager. My school, Bristol Grammar, considered itself a minor public school in character - I guess I never bought into that, working-class kid that I was. I played guitar in a band in my first year at Warwick University, but also attended soc-soc meetings (socialist society). I was amazed that I had no idea what they were talking about! The vocabulary and acronyms, as well as some of the views about the Soviet Union and China were just totally new. Still, I studied hard.
I joined the International Marxist Group youth organisation towards the end of my first year, and the IMG proper a little later. At that time, the IMG was the British Section of the Fourth International and Tariq Ali was one of the leaders. He was generally considered rather emotional and not a truly rigorous thinker, and the real leader was a guy called John Ross (until recently economics advisor to Ken Livingstone, the former Mayor of London!). We did the usual stuff: endless demos, lots of planning, selling the paper. I have a collection of "war stories", like the day we nearly occupied the Chilean Embassy.
I dropped out of the IMG (now the "International Socialist Group") when I was around 26. I guess the whole thing had ceased to be a novelty and somewhere I had lost momentum. I probably still accepted Trotskyism as a broadly correct social theory until my early thirties. The definitive end of that view was when the Soviet Union crumbled to capitalism. A leader writer in, I think, the Guardian, wrote that the fall of "communism" (Stalinism as we thought of it) would definitely sink Trotskyism too, as Trotskyism was sustained by its belief that a "workers state in transition to socialism" was the inevitable successor to Stalinism in Russia. Tariq Ali reported in his obituary of Ernest Mandel, the leader of the International, that Mandel saw the event too as postponing communism in the classical Marx-Lenin sense for "500 years".
I think Marxism impressed me (as it did a lot of people) because methodologically it analysed societal "structure" as routinised, stabilised patterns of human relationships. This just seemed a deeper analysis than the superficial model-building of "bourgeois social science". However, such an ethnographic model of society is no longer the sole ownership of Marxism. It turns out that the tradition of Marx, Lenin, Trotsky conflates a number of trends into one overarching scheme, which is empirically not correct. But it is wonderfully sophisticated and complex! I still recall "History and Class Consciousness" (Georg Lukacs, Merlin 1991) as one of the most inspiring books I ever read.
I have a familiar problem with politics. People take gratuitous moral stands. I tend to see the global human condition more as the dynamics of particularist social groupings, some of which are organised states, some more informal, each expressing their own interests in cooperation and/or conflict with the rest. None of the groups with real power and responsibility take a universalist view of their mission. Yet a partial view by its very nature devalues the interests and even the humanity of groups which "get in the way". This is the slippery slope which can lead to arbitrary bad outcomes for the "bad guys", and interest groups tend to be rather selective about which other groups they choose to demonise. The Nazis always make an easy target because they were pretty bad demonisers in their own right, and they're not around any more in any strength to argue back, or to be accommodated. Other bad things have happened since the 1940s.
It's easy to see why it's in the nature of specific power groups to ruthlessly pursue their own interests, cloaking their self-interest in a spurious cloak of universality. It's less easy to see what can effectively be done about it, except at the margins.