You probably aren’t interested because you have made up you mind already, but are you aware that the use of the watermelon smiles etc was in an article to satirise the kind of attitude that would use those terms? An article critical of outdated colonial attitudes.
BoJo had his gaffes covered with kid gloves, the BBC going so far as to pass off obviously fake footage to make him look competent. Despite his talk of "watermelon smiles" and "picaninnies", or the horror Tory policies had inflicted on Britain's vulnerable, or the srious, international lies Johnson was caught in, the BBC gushed on how affable and charming his persona was.
I would love a quantitative analysis, but I don't need one to see the truth. They can't be trusted much more than the Daily Mail or The Sun.