Here's my take on the issues in this thread:

Martial Arts for a 3 year old
At this age, martial arts or other sports activites for this age are about (a) parents fulfilling their own dreams through their kids and (b) fun activities for the kid. For example, mom or dad really likes a particular sport or activity and so gets junior involved. If mom or dad really wants junior to continue the activity, they best make sure that it is fun for him or her. (Sometimes mom and dad have different ideas about what sport junior should be enrolled in, but that's a different issue.)


Trusting Strangers (versus Friends), and Parental Presence
Strangers are not to be trusted. You expect them to conform to the rules of a polite society (and should be polite in return); however, you keep your distance from them (physical and in conversation), just in case they don't. When you get to know someone, he or she can become a friend (and trusted). Normally it takes time to build a friendship, but sometimes the process can be faster if a parent or other really trusted person vouches for them.

A stranger is a stranger, whether or not a parent is around.
A friend is a friend, whether or not a parent is around.

And there are some rules of behavior that apply to everyone, even friends and family. Private body parts remain private, even from friends.

Forcing Kids to Be More Familar with Someone
If a kid doesn't want to talk to, hug, accept gifts from someone that a parent wants her to, the kid should be empowered (both taught and allowed) to decline politely. And hiding or scowling is not polite.

-Kuovonne