"Harm" is essentially circular logic. Assuming we are acting logically, the only harmful theory is a wrong one. And so when speaking of harm, you are assuming the correctness or incorrectness of some theory. This is why having a free and open society where any theory can be comfortably pursued to its natural limits is absolutely critical. Everything should be being constantly challenged to ensure that we aren't just falling into a new dogmatic cycle, as history shows we ultimately always do.
Beyond this I'd also add that many 'rock solid' theories do contradict each other. The obvious example being relativity and quantum mechanics which have mutually exclusive things to say on countless topics ranging from black holes to the nature of time itself. Both work phenomenally well and have abundant evidence in their own bubbles, but side by side - they can't both be true in their current state.
I can't think of any examples where this is the case currently. A historic example would be genetics. There's little doubt that
genetics influence near to every aspect of our competencies. And that's extremely useful information that can help improve life and society in countless ways. It only became harmful when a man decided to take it to an illogical extreme, predictably creating a very real dystopia in his fanciful efforts to create a very distant utopia.
Beyond this I'd also add that many 'rock solid' theories do contradict each other. The obvious example being relativity and quantum mechanics which have mutually exclusive things to say on countless topics ranging from black holes to the nature of time itself. Both work phenomenally well and have abundant evidence in their own bubbles, but side by side - they can't both be true in their current state.