Why do dads not come around to see there kid(s)??

My son's father has been in and out of his life since he was born. He will not stick to a set schd. He thinks he can come around when it's only good for him. I'm so sick of the excuses & most of all I'm so very sick of him blaming me. I keep him away I don't let him see him, I use him as a pawn he says. Are you kinding me I have all the emails these last few months for my proof of ME emailing him asking him to lets work out yet another schd. for him to see his son (as I said i am emailing him asking him) through email cause I will not meet with him in person. He will not email me back or he emails me back saying something nasty to me. I have even emailed him a proposed schd. asking him if he could agree to it. Have not heard. He just sends me tex msg's. from time to time asking me if he can see his son & I used to respond by saying yes of course as soon as we can work out a set schd. and then he never gets back to me. Am I wrong to not let him come around without a set schd.?