very thoughtful topic.
first I assess the people involved. I'll pass any behavior if I think my commenting will stir a violent response. I'll snap a pic and report them when my trip is over. First rule: nothing is worth sacrificing my peace or safety. Second rule: regardless of what I feel about wilderness ethics, if behavior is not illegal or violating local restrictions/rules, I'll mind my own business.

now to specifics, but again i'm generalizing my response - situations dictate different responses, and also whether my cell phone works. If I have cell reception I always pack it. In this case I can report really off behavior to rangers.

And the activities we identified;

1.Building a new fire ring - usually ignore - A. just not worth it to me. EXCEPTION: fire danger high and fires are prohibited - then I mention it to the offender and say I'd appreciate it if they comply with the restriction.
2.Chopping up or down a tree for fire wood. actually I think I might just pass by and forget it. dunno; I haven't seen that yet except on land where it's legal. A/F
3.Hiking with a dog where it is forbidden: B, then what they do with that is probably next time. F also if I think fido presents a real hazard.
4.Fishing with bait in a fly-fishing only stream. C/F. This one I see often and it really gravels my gut.
5.Feeding wildlife. A unless they are baiting game illegally, then D and F. I rarely confront poachers and illegal hunters directly. Can be very unhealthy; they know good and well what they are doing and they won't listen to me.
6.Leaving a fire or coals unattended. C and E. I will ask them to finish dousing the fire or please not leave it unattended; if they leave the fire I will not - I'll finish putting it out myself.
7.Littering - honestly most of the time will be A (shame ...), but sometimes I'm in a "had enough" mood and will go C.
8.Hiking in a group that is larger than allowed - A, D, F. I won't confront the group unless I see that the clear leader of the group is approachable, then I'll simply ask if he/she is aware of group size regulations for the area.
9.Camping in an illegal area or illegal/closed campsite - just F.
10.Mining with a pick and shovel - If approachable, B and F, but always F.

Admittedly I will try to see my way to avoid confrontation as much as possible. Gross violators may just not care to the point that it isn't worth my while ... I will take corrective action myself if the safety of the forest or wildlife is in jeopardy. Unfortunate, but we just can't "fix" all the transgressors in the world, and often we are powerless to bring them into accountability.