He is close to the truth in that most professing Christians can't give a concise accurate reason why they are a Christian. Some think it is because they were born into a Catholic family, some because they believe in God, some because they go to church services every Sunday. None of those things make one a Christian though. One must believe Jesus Christ is God, He came in the flesh and died for our sins, rose again in newness of life, and ascended to heaven to be our Advocate and Intercessor before God's throne. Being born again is a necessity as was told to Nicodemas by Christ Himself. Glenn Beck might be right on that account, but I would not go around repeating everything that he utters on his program.
Christian or non-Christian aside, I find Glenn Beck to be a self-aggrandizing boob. I don't take much of what he says seriously, and his frequent references to Nazi Germany qualify as a drinking game.
Well it is true that most "Christians" aren't even christians. Acts 11:25-26,"the first disciples were called christians" So in order to be a christian, you must be able to call yourself a disciple. and to be a disciple, you must follow Christ, and to follow Christ you must know Christ and know what He did for us. the sad part is, most people think that all they have to do is believe in God to be a christian, so those "christians" don't know who they are in Christ, but as for true christians that take up their cross daily, and live like Christ does, yes we know who we are in Christ