Upon what do you base that? Is there a study somewhere that supports the idea that earplugs are dangerous? If there is you'd better let the folks who write and enforce worker safety laws know.
I think the inference there is that you can't hear what's going on around you, i.e. cars coming up behind you, dogs chasing you. It's the same reason why many of us don't like riding with our MP3 players/earbuds on. Less pontification, more switching to decaf.
I've noticed the same thing. Mine is a microfleece ear warmer/sweatband from Pricepoint-
http://www.pricepoint.com/detail/20191-510_PNTHB9-1-Clothing-2-Cool-Weather-Gear/Price-Point-Headband.htm.
Definite reduction in wind noise when over my ears.