Look at Einstein’s Relativity or the works of Sigmund Freud who does not at all come across as a ‘Freudian’. As a system ‘Freudianism’ is a bit discredited, I think of Otto Kernberg railing against homosexuality, but Freud himself refused to do conversion therapy because psychoanalysis could only increase the capacity for love, not diminish it. Therapy has moved on (Rogers, Bowlby, Kohut, Beck) but in Freud you often find zingers (his analysis of sadism) that seem valid outside of his system. With Freud (and even more so Marx) people’s objections are often to the content not the style.
When a group becomes hermetic though it can degenerate to people hearing dog whistles and barking, which makes you a dog.
‘Truth’ is a dangerous concept in rhetoric and logic because of how it works with negation. I was told by a science teacher to never say “to tell the truth…” because it presupposes that I lie. A 9/11 truther is a lunatic’s lunatic. Kurt Gödel shows how much trouble you could get into with a function T(x) which determines the logical truth of a logical statement.