When conflicting information is encountered, the mind enters into a state of cognitive dissonance. In this state, the mind seeks to relieve the discomfort, usually by (a) denial, (b) action, or (c) accommodation. In practice, the last option is generally the most mentally expensive and painful, especially if it involves rewriting or downgrading the self-concept. Accommodation is about restructuring the mental model, worldview, or schema-set to support new information. For the example given in the question, this process is likely necessary as the father's worldview must be updated to accommodate the new data. Since worldviews are comprised of a complex web of interconnected mental schemas, this process can take a while and involve fair stress.
Accommodation can be broadened beyond mental knowledge, beliefs, and values to include social restructuring, where relationships, affiliations, and maybe laws and institutions are reconfigured. That is, both individuals and groups may undergo periodic revision when encountering internal contradiction.
On the matter of ethics, one of the key features of mental or systemic restructuring is cost. We might say the process brings temporary dysfunction and distress. If we assume utilitarianism based on minimising distress, then there appear to be at least two core factors:
Entity scope -- the causal or mental boundaries of being, or the circle in which suffering is measured.
Time horizon -- the temporality, or time-span, in which suffering is to be minimised.
In the short-term, highlighting contradiction and other conflicting information can be expected to bring more suffering than wellbeing. Similarly, say in the case of violence, protecting the will of one entity may go against the will of another -- thus shifting or reallocating suffering from one place to another. On the other hand, if we broaden the scope of consideration, different measurements may unfold. By measuring longer-term, the net effect may show overall increased wellbeing. And by measuring both the victim and aggressor together, we may find that preventing violence lowers overall suffering. These net benefits are especially likely if care is taken in mode of delivery.
In general, resolving morally significant ignorance is net beneficial. But often that benefit requires using larger entity scope and longer time horizon. So remember to consider the broader set of affected parties, as well as the longer-term. Furthermore, remember to consider the available ways of deliverance.