Winston Churchill was racist. Or perhaps, more accurately, he was England centered. He was one of the men who oversaw the collapse of the English empire as it lost all of its holdings throughout the world, and English leaders were (and are) notoriously nationalistic. He was fiercely proud of England and being English. Of course, it is hard to lead a country if you aren't pretty nationalistic. I wouldn't elect a President who isn't committed to the interests and success of the United States in the world.
In addition, Churchill was a Master statesman. He knew how to interact with other nations and cultures in a sensitive and politically wise way. It is one thing for him to make a comment about how the English pronounce words for an English audience; whether he would say the same thing to the French foreign minister, or in front of the French press is something else entirely. As a brilliant statesman it is inconceivable that he would make this statement in a way that was meant to offend.
At the same time, we must be careful about trying to evaluate historical figures by current cultural standards. The 21st century is a totally different world. First of all, with instant and constant communication, everything we say is immediately available to everyone. A politician today can't have an opinion about anything because someone, somewhere will read what is said and hate him for it. And that is another problem. In the 21st century we have become so finely attuned to anything that isn't antiseptic and sterile. Today, even an accidental slur is front page news and an epic offense. (unless you say something against white men, that is always ok.) In Churchill's time nobody got upset if somebody busted your chops.
But really, if you read enough by Winston Churchil, and he wrote a ton, you will discover that this kind of statement was humor, and he was hilarious. He would make this kind of obviously pompous statement to get a laugh. He was English, he spoke English, and when he mispronounced a foreign word, people would get on his case. He saw this as the absurdity it was. Of course people mispronounce foreign words... what is the big deal? So when he was accused of mispronouncing a foreign word, he cut through the silliness of the accusation and said, "It is the inalienable right of every Englishman to pronounce foreign words exactly as he pleases."
Have you ever made a tech support call and ended up in a foreign country?