President Obama -- Smiles Like a 'Split Watermelon' ... British Anchor Says (VIDEO)

President Obama smiled "like a split watermelon" when Pope Francis visited the White House ... according to a British news anchor who is now getting a crash course in racist stereotypes.

Channel 4's Matt Frei used the unfortunate turn of phrase on-air during a taped report on Wednesday about the Pope coming to America.

Frei pleaded ignorance when the inevitable social media backlash began, claiming ... "It was intended as an entirely innocent phrase that apparently has a history I simply wasn’t aware of."

Dear Matt,

To be safe, please also refrain from quips about poultry ... when talking about our President.

Sincerely,