Annoyingly Polite

There is this guy at work, if I had to guess his age, I would give him the benefit of the doubt and say that he's around 60.  But I would honestly be surprised if he was any younger than 70.  Anyway, when I first started working here, approximately 5.5 years ago, I thought he was the nicest old man in the world.  He ALWAYS spoke to everyone, by name.  If you slowed down, he would talk to you, try to learn something about you.  Me, being the young naive sweet thing I was (bwwaahhhhaahhhahhahhahha), I would talk to him from time to time.  Well, one day, he asked me if I wanted to have dinner with him.  EVERYBODY HOLD UP: this man is older than my mother (maybe), but as old as my mother.  He's pasty.  And he thinks I want to have dinner with him.  See what I get for being nice?  So now, when I see, I pick up my pace.  Yet, every single time I walk by him, he says, 'Hello Danielle', to which I say hello back, never breaking stride.  Then, he must squeeze in, 'Have a great day'.  Now, typing it out, it doesn't seem that bad, but by the time he even begins to say 'Have', I'm almost out of site.  Just the other day, I saw him as I was going in the restroom, we had our typical exchange.  I saw him as I was leaving the restroom, and he had to say hello again???!???!?!?!  Excuse me sir, I just saw you, not even a minute ago, you don't have to keep speaking to me.  Act like you don't see me, especially if your back is to me as I'm walking by you.  It's ok to not speak to someones back.  In fact, if I'm not looking in your direction, don't feel obligated to speak to me.  Aghh, at first I thought he was just a nice polite old man.  Now, I go out of my way to avoid talking to him...