There are many ways in which Holden shows himself to be blind. Let me offer three ways.
First, one of the things that Holden constantly says is that people are phony. He can see (sometimes with great clarity) that people are often fake. However, he almost never sees that he too is phony. In fact, this almost never crosses his mind. In this sense, he is not only blind, but also a hypocrite.
Second, Holden is lonely. This is why he longs for companionship. However, in his endeavors he fails to realize that the reason why he does not have relationship is also because of his attitude towards people. He is not a character that is pleasant to be around. He is blind to this fact.
Third, Holden often fails, but he is the one who sets himself up for failure. What is even more ironic is that he takes pride in this at times as well. He probably does this to get attention, but he fails to see this as well.