These weren't exactly "private" to begin with, but no they weren't then. There was a time before he worked with Marvel where I believe he brought them up on his own accord (I believe in an interview?), apologized for them, said he was going to move on from that kind of tweeting, and low-and-behold he did. Since working with Marvel, I don't know of a single blemish to his name from the Twittersphere.
I do not have the source at this time. This has been mentioned by others on a couple of media outlets that I saw. I just do not like that Disney is playing the card of innocence that they were completely oblivious to these tweets, and if they were then their ineptitude needs to speak much louder than this.
On the Dave Bautista thing, I wonder if Gunn himself might phone him and say: "Hey man, look I appreciate what you're doing for me, but I want this film to happen even if I'm not a part of it, and I want you to be a part of it. It would mean the world to me that my baby can be completed, and I want to see it through with Drax including into Avengers 4. Do your best to stay on the project man, I'd really love that!"