In a discussion surrounding tweets made by US President Donald Trump where he had told four Congresswomen to "go back" to the places "from which they came", Munchetty implied the messages were "embedded in racism".
Turnbull says Munchetty was “within her rights to do what she did and I thought the ruling was wrong.“
While it was originally ruled that Munchetty, 44, had breached BBC guidelines surrounding impartiality, BBC director-general Tony Hall overturned the decision at the end of last month.
Turnbull, who presented the programme from 2001 to 2016, has now said the initial ruling made against Munchetty was "unfair".
He spoke about the issue to Yahoo UK in an interview for his upcoming Channel 4 documentary, Bill Turnbull: Staying Alive.
Turnbull shared: "Naga’s an old friend, I’ve worked with her a lot. In my personal opinion I know the BBC has its procedures it has to go through and that sort of thing but my view was that she was within her rights to do what she did and I thought the ruling was wrong.
"The difficulty is that if you get a ruling against you it might feel like a mild form of censure but it gets in the papers, it goes on the internet and there is always that mark against you: ‘Oh, but they were told off by the BBC.’
"Every time someone writes an article, 'in 2019 this happened' and I thought that was not fair to Naga and I’m very pleased that that’s been reverted."
The Classic FM host also spoke about how a complaint had been made against him years ago which proved to be false after a thorough investigation had been launched by the BBC.
Turnbull went on: "The BBC has this responsibility so years and years ago when I was on Breakfast on the weekends, this was forever ago, someone thought they heard me say something like shooting and eating squirrels or something like that was a good idea, which I had never said. One person.
"So, the BBC had to go back through everything I said for six months, everything I said before, they found out that I hadn’t said it and it was actually somebody else, a guest had said it on the television instead. A whole investigation.
"So that’s what they have to do, but I’m very happy for Naga, that it’s been turned round."
Turnbull made an emotional admission last year following his appearance on The Great Celebrity Bake Off for Stand Up 2 Cancer as he revealed he’d been diagnosed with advanced prostate cancer in 2017.
Later this month, viewers will see him in his own documentary, Bill Turnbull: Staying Alive which charts his life following the diagnosis and sees him explore the different treatments that are available to cancer patients.
The documentary will air Thursday 24 October at 10pm on Channel 4.