What if the truth screams as loudly as a male barn owl crying for a mate- This is saying, what if the truth is so obvious that it is impossible not to hear, like a male barn owl crying for a mate. and we miss it because we have not allowed ourselves to listen to the channel it's on -- or we've tuned it out? - Imagine a situation in which we are watching television and on the television is "the truth", but we are watching a different channel , or we are just not listening to the channel (we tuned it out) So the sentence is basically saying: "What if the truth is very obvious, but we just aren't listening to it"