Coyotes are highly intelligent and they know a bigger predator when they see one. We have eyes in front, and sometimes I think we may be a terrifying sight to many animals due to our lack of facial hair - which may help clue them in as to our intent. Eye contact among the higher animals is a primary communication - long before we get close enough to be sniffed for gender.
We also show our teeth more than any other animal - which probably doesn't come across as a smile to wild canines. Just watch the reaction in a pack of wolves when the big guy shows his chops. Others instantly react like our own domestic dogs by tail wagging and cowering. Well, maybe ours don't cower because they know that we don't bite much, but there's the picture. When we make eye contact with our dogs, they usually react like a lower ranking pack member - as well they should.
It's the same with wild dogs except that they usually leave the area because they aren't in our pack.
Also, coyotes have been ruthlessly hunted for at least two centuries on this continent. Being smart, I'm sure there has been some generational info passed on to their young. It's normal behavior for a coyote to give up his meal to a human because of the huge size difference. There are many accounts of humans walking right up to a feeding group of wolves and doing the same thing.. Wolves and coyoyes will wait their turn at a kill until the humans have left.
The only animals in North America that will defend their kills are the bears and big cats. But, even they will usually make themselves scare if a human approaches. Animals seem to respect head height, not body mass. Eyes in front and up high means power.