The phrase 'As Blind as a Bat' refers to someone who is unwilling to recognize bad things, or someone who is completely blind.
You can use the idiom 'As Blind as a Bat' to describe someone who refuses to notice an obvious thing.
Example of Use: "Will is so in love, he is as blind as a bat when it comes to Kate's rude behavior."
Though some species have poor eyesight, particularly during daylight hours, bats aren’t truly blind. However, this wasn’t common knowledge in the days of the origin of the idiom 'as blind as a bat.' The term is attributed to a similar one by the famous Aristotle; he wrote: “For as the eyes of bats are to the blaze of day, so is the reason in our soul to the things which are by nature most evident of all.”