My interest in Marxism was not just political but intellectual as well -- those two were inseparable. It didn't cause me problems on a day-to-day apart from when the university management tried to alter my conditions of employment! I think in some ways I was very fortunate but the liberal ideology you write about is very much a real thing that has to be constantly interrogated. As for organizations, my IRL comrades in the trade union were essential but I think it is vitally important to not place oneself in a position where you are at legal risk (if organizations are illegal I would be cautious as whatever organizations exist are almost certainly monitored or infiltrated) but the internet can be a great resource. I also think a certain degree of intellectual independence is not the worst thing in the world as all too often organizational fidelity can come at the cost of your own thinking.
SOMEDAYS YOU JUST CAN'T GET RID OF A BOMB