"But though I be rude in speech, yet not in knowledge..." (2 Corinthians 11:6)
Try this sometime: before you say what's on your mind, think through your list of synonyms for whatever big word your about to use—the one that's both going to prove your point and also make you look smarter—and use a smaller one. It would seem that's exactly what Paul is talking about here. That word "rude" in the King James doesn't mean "rude" as in "impolite". It's referring to a simpler, less pretentious and more direct way of speaking. While the Greek word translated "rude" is idiotes (obviously giving rise to idiot), it actually means "uneducated" and "ignorant" (nescient even, but we won't go there). It's the "rude" of rudimentary. Paul is basically saying that he's a whole lot smarter than he lets on. And while he was a cultured Hellenistic Jew, conversant in Hebrew as well as Greek, he was also a simple tentmaker from Tarsus (see Acts 22:2-3). He played both sides of the superfluous intellectual field.
How rude?
It means a lot to God that you take the time to make yourselves available to any type of person out there. And if you make a conscious decision to be used of God to reach the widest possible audience, you will find yourselves interacting with scores of personality types who would each hear the gospel of Jesus Christ (if they haven't already) in your own words. Just make sure it comes through in your behavior. Really, one of the ways to prepare the soil, so to speak, is to actually listen to yourself speak. Know how you come across. If you can say the same thing with a few simple, spare and choice words rather than hunt for the obscure adjective that you think will enthrall the person with which you're conversing, please do. The language of the Gospels were written in everyday layman's Greek. Nothing fancy, nothing flowery, yet imbued with all the power of Heaven.
"And my speech and my preaching was not with enticing words of man's wisdom, but in demonstration of the Spirit and of power: That your faith should not stand in the wisdom of men, but in the power of God." (1 Corinthians 2:4-5) Yes, you don't want someone latching on to you through your charisma and intelligence. You genuinely want to hook people up to God.
Words like love, compassion, mercy, forgiveness. People know what these words mean (or they think they do). It's the qualifiers and packing material with which they're delivered that cause confusion. That, and a little thing called hypocrisy. See, many people nowadays have "heard it all before". What they haven't seen, however, is true love, lived out. Each individual running this way and that, spouting off a half-realized message of redemption and forgiveness is not what Jesus had in mind when He said "Go ye into all the world, and preach the gospel to every creature." (Mark 16:15) Jesus' message of Heaven doesn't need our intellectual underpinnings to cause it to bear fruit. It needs our commitment and our simplicity lived out. And when Paul says he was "rude in speech, but not in knowledge", part of that knowledge was knowing how to get his point across to whomever he was speaking in a way that was intelligible to them. God is the one who validates us on the inside. Knowing this, we are able to lay aside any ways of thinking and talking that will only end in alienating those who are less than inclined to listen to hyperbole.
"Speak properly, and in as few words as you can, but always plainly; for the end of speech is not ostentation, but to be understood."
-William Penn