He is on average right. If you are purposefully not showing body language, then you may very well be making people uncomfortable...which may very well be your aim.
My aim is to get people to focus on my words, which I have selected with great care to convey my meaning as precisely as possible. I don't know what signals my body language might be conveying, so yes, I do my best to suppress it in the interests of avoiding mixed signals. I will sometimes use vocal inflections and pacing, however, for specific purposes such as highlighting certain points, conveying humor, building (or dashing) expectations, etc., especially when speaking to groups. It is easy for me to maintain a relatively neutral speech pattern as well, though. I don't know if this makes others uncomfortable. The only direct feedback I have received is an occasional observation that my nonverbal cues are very hard to read.
Hogwash?
Nonverbal communication represents two-thirds of all communication.[1] Nonverbal communication can portray a message both verbally and with the correct body signals. Body signals comprise physical features, conscious and unconscious gestures and signals, and the mediation of personal space.[1] The wrong message can be established if the body language conveyed does not match a verbal message. Nonverbal communication strengthens a first impression in common situations like attracting a partner or in a business interview: impressions are on average formed within the first four seconds of contact.[1] First encounters or interactions with another person strongly affect a person's perception.[2] When the other person or group is absorbing the message they are focused on the entire environment around them, meaning the other person uses all five senses in the interaction: 83% sight, 11% hearing, 3% smell, 2% touch and 1% taste.[3]
http://en.wikipedia.org/wiki/Nonverbal_communication#Importance
I have read several similar claims, and still disagree. Consider the following example conversations:
1. My student and I discussing the experiment he conducted yesterday
2. My SO and I considering vacation options for the upcoming summer
3. A friend and I comparing notes on a movie we just saw
I fail to see how in any of these conversations more information is conveyed nonverbally than verbally. Just how do I use body language to say, "You should repeat this measurement with the old sample," or "I'd like to go somewhere we can hike", or even "this remake is even better than the original". Perhaps I am unusual, but if you are speaking to me and not listening to my words, there is absolutely no way you are getting anywhere near two-thirds of my meaning. Moreover, the meaning you infer is probably wrong.