It wasn't that Ron hated Malfoy anymore, it's just that he didn't understand, why Harry, his best mate would want to be with the amazing bouncing ferret and why they wanted him to start calling him Draco.
He'd grown up. Well it had been Hermione threatening to make him sleep on the couch for a month and he knew what that secretly meant, if he didn't "Grow up, Ronald! I know you don't like Draco but you should try and be civil for Harry."
So he had, and while 'being civil for Harry' he found out that Malfoy (so he didn't hate him anymore, that didn't mean he'd start calling him Draco anytime soon thank you very much) wasn't a half bad opponent for chess and he supported the Chudley Cannons.
And even though Ron figured he might admit that Malfoy was a friend if tortured or subjected to veritaserum. He would never get used to Malfoy sitting in the burrow blowing raspberries to his daughter, before helping his mother, cook the dinner and having civil conversation.
And after when he was lying in bed next to his wife, and remembered the way his best mate practically beamed when he'd asked Malfoy for a game of chess, and how he'd accidentally seen a private moment between Harry and Malfoy talking, while Malfoy looked at Harry like the world shone out of his eyes.
Maybe he could see what Harry saw in Malfoy and maybe it wouldn't kill him if he started calling Malfoy, Draco.
For Harry, obviously.
Not because he liked the git.