I have a fixed gear, road, cyclocross and mountain bike. If I end up in a precarious situation, the bike I would most be confident in riding out of the ordeal is my fixed gear because I feel like I have the most control over the bike. The drivetrain is directly engaged with my legs, so I am able to not only modulate and control my speed and bike with the brake, but as well as my legs. I might not stop as fast as my cyclocross bike with the stupid powerful mini-v brakes, but I feel like I am in more control. Maybe stopping super fast isn't the best thing to do, maybe whipping my bike into a different direction would be safer and the nippy and quick handling of most fixed gears bikes would help with that.

Your dad's friend probably gets his opinion from when he see's the ill-fitting gaudy fixies where the owner has no idea what their doing then ride similarly in correlation.