Actually it's the opposite. BBC political pundits/reporters are supposed to be impartial. BBC sports presenters can think and say what they like in their free time.
I guess they don't all have the same concerns about humanity as Gary?
BBC employees in the news and politics divisions have to be seen to be impartial. But Gary is a sports presenter, so is free to express his opinions.
His comments on current affairs and political views are separate from his job. After the fuss about him comparing the language surrounding 'the boats' to pre-Nazi Germany, the BBC made it clear that he was free to continue to comment.
After the last nonsense, he's well aware of what he's allowed to post about and what he's not. And as a sports broadcaster he certainly does not have to be impartial about politics. Some things are more important.