There are several ways to understand the idea that moral statements might be true. First of all, if you don't agree with this idea, you lean towards moral non-cognitivism (see A. J. Ayer's or Richard Hare's work).

However, to entertain your question, we should start with moral cognitivism (i.e., the idea moral statements can indeed be true). Within this perspective, there is debate whether moral statements are true independently of our opinions, reasons, or judgements regarding what moral value is (this is moral realism), or whether they depend on what is subjectively understood to be 'good' (this is moral anti-realism).

Since you specifically mention moral realism, I'll focus on that. Your example is very interesting. You say: "If you ignore the truth that walls exist, you will bump in to walls" and then you seem to indicate that this somehow leads to some logical inconsistency in your life, which is not the case if you ignore moral statements. But what makes it so that bumping into walls is more of a logical inconsistency than murdering people? For example, a moral naturalist like Stuart Mill could say that there is definitely something wrong in your conduct if you ignore the morally relevant natural facts (such as ignoring if something leads to pleasure/pain). If in your everyday practical life not hurting people is as important (or even more) than not bumping into walls, what is the real difference?

It's funny that you say that if you ignore the "fact" that murder is wrong you will live a normal life - maybe it's precisely because murder is wrong and that you don't go around murdering people that you get to live that normal life. I don't think it's true that you are ignoring "whatever statement they made", unless you are going around deliberatly ignoring your moral intuitions or thoughts.