I've ran across that quite a bit here in Mississippi, which to me is a little surprising seems how there is that mantra about the south and people being more friendly. Sometimes it may be as simple as some are jealous of what you have as well. I give a "wave" to all bikes, but there are times were I'm in another world when riding and some wave to me and I don't see them. I'm not trying to be a prick, just didn't see 'em.
Then there are times when you run into situations like I did here not long ago. I had to go to a local bar to pick up a friend. There are quite a few people that ride that hang out in there, I was sporting a H-D t-shirt and this big 'ol dude comes up the me and the conversation went like this:
Him: What's your shirt say? Trying to be a wise guy
Me: Harley Davidson
Him: Well it would be nice if you had the bike to go with it!
Me: I have the @#$%*&% bike to go with it!

Him: What did your daddy buy it for you?
Me: (blood pressure through the roof now) Nope, for your information I bought it and paid cash for it on my own with what I saved while in Iraq.
Him: Oh, thanks for serving and it's to bad you don't ride with us.
Me: laughs and says who would want to ride with an @$$hole like you.
Him: Turns around and walks off
Come to find out he just got his first Harley about 3 weeks earlier and the owner of the bar is the one that paid for it.
Like the saying goes- There's at least one in every crowd.