The definition of "truth" in general isn't the question, necessarily; it's that it could be as simple as "does a shoelace contain 98% or 97% cotton?" or something as serious as "is the government circumventing citizens' rights without our knowledge?"
One of those might be worth sacrificing our societal well-being to know, the other isn't. Unless the definition of "truth" is restricted in some way, the answer is going to be subjective.
I
guess , but I don't think the question necessarily precludes our ability to separate valuable truths from useless truths. Like you keep saying, it would be silly to put society in jeopardy over Richard Nixon's favorite flavor of soda, but we can recognize that in any case.
The cure for cancer, on the other hand, is a truth worth pursuing, even though finding it would have massive implications for a lot of businesses and some working people. People would lose their jobs. But it's still worth it.
So, there's the "restriction," I guess. We use our best judgment to pursue
valuable truths--truths that will overall benefit society in the long-term, while perhaps sacrificing it in the short-term.