No, not really. You need to look at the risk pool (number/miles covered by peds/trailers).
I have a trailer for my little un. I have ridden it on the road a bit but will do this more out of necessity and generally choose off road if I can.
Having said that I did 44 miles on roads over in France last week with the trailer (same one as Ianaruk's) a 21kg youngster and a fair bit of kit. Averaged just under 13mph over 2000ft It is true that car drivers generally give more room.
Risk is a funny one and I think it's more of a head thing that a real thing. I can't really put my finger on why I perceive the trailer to be less safe around traffic than a child seat on the back of the bike. Anecdotally I had an insanely close pass (I would say deliberate) when I had my daughter in the bike seat last year on a really quiet road. I haven't had one insanely close pass with the trailer.
See, if I had to carry a child, I'd far rather have them in a trailer than a seat. The seat raises the centre of gravity of the bike, and if I had to stop quickly, or swerve, or fell off, the seat would make the bike more likely to topple, and if the bike went over, the seat goes with it. A trailer keeps the weight low, puts the child in a roll cage, and if the bike falls over, the trailer says unaffected.
Drivers tend to pass wider vehicles wider. A trailer widens a bike, a seat doesn't.
If a road is very bad due to bad driving, should a parent be cycling on it anyway? Losing a parent is a pretty bad experience, what right does anyone have to perhaps inflict it on their child?
Yes, risk is to a large extent a head thing, and I do get people's worries. But everyone I know who uses a trailer is happy about it (obviously, or they wouldn't do it). The only way to avoid all risk is not to have children!