+1x1000! Couldn't agree more. When I met my wife 4 years ago I was cycle-commuting in an urban enviornment. She posed the question of danger. My reply was that I'd been doing fine for over 15 years, so all of I sudden I meet her and it becomes dangerous? We agreed she'd go w/me on my commute on a Saturday(less traffic). She said she was nevous at first and then after a couple of miles she said she calmed down as I was so confident. I was riding behind her to her left, slightly the whole way. We ride to church together now that we live rural and she's ridden the 12.5 miles to our old church several times by herself. She's riding clipless now and loves her bike. We've done weekend tours together and ride the 6 miles to our new church, frequently. My daily commute is 40 mi rt and she never brings up the 'dangerous' aspects, anymore as she's an experienced, confident cyclist now.

I guess what I'm trying to say is that ignorance and/or inexperience inspire fear. Get a worthy bike for your co-worker and have him ride your commute w/you on a light traffic day or agree to go from his residence to your work w/him by bike to show how most of the danger is in his imagination. The least you'll do is build a healthy respect from him for what you do. If he wont agree than you've every right to discount his opinion as invalid and let him know that. It, also sounds like there may be some jealousy as people often are critical of behavior that doen't fit into their standard of normalcy.