Unless they research the topic honestly, as I do.
Here's what often happens for me on this board (and not just on the board). Someone makes a claim like you did: there are fewer active shooter events than whatever it was. That seems incredibly fishy to me, so I go look it up. And I learn something: "active shooter" events are actually rarer than I had thought. I also learned something else: "active shooter" events are more narrowly defined that I thought. In those cases, the new knowledge happens to balance out with respect to this issue.
In either case, though, I learned something. That is, I corrected for my bias. I still reach the same conclusion as I had when we started, but that's not always true. It's more true now than, say, two decades ago because I've been doing this for a while and so I just know more than I did. Less surprises me, and so I revise my views less. But it still happens.
When I was younger, I used to be a free trade skeptic. Then I read about trade economics, to see if my view was correct. The evidence was overwhelming against my position. I am now a free trader, even though that's not exactly a "liberal" position. I have also been extremely concerned about raising the minimum wage too high, for fear that it could decrease employment if it becomes higher than the marginal product of labor. But in recent years, there have been studies showing mixed effects in this regard. So while I'm cautious before endorsing just any minimum wage hike (One of the few leftist Dems in Congress proposed, I think, something like a $22/hr minimum nationwide, which is ludicrous), I'm less concerned than I was. I still believe that "phase-in" doesn't really solve the problem.