I'd probably turn them in, if I knew their license plate number and could remain anonymous...
but I do understand your concern of revenge taken upon you by the perps....
a hunting partner and I witnessed an illegal deer kill on the Snoqualmie unit, about 22 years ago. We talked to the gammies at the Spur 10 gate and they apprehended the poachers upon their arrival to the gate going home with an illegally harvested doe, hidden under equipment/tarp in the back of their pick-up truck. Pretty obvious guilt, 'ey??
we had to write down our accounts & witness of the illegal kill made just down the hill from our stands that morning. the gammies separated my hunting partner and I when we wrote those statements. The gammies then each seperately reviewed our statements, reinterviewed us verbally and added charges to the detainees...as the now handcuffed poachers were looking at us and standing by the WDFW vehicles at the spur 10 check site. A King County sheriff car was there too. The charges/case went to Issaquah Superior Court a couple months later. The poachers settled for a wrist slap. The prosecuter said our written and verbal statements weren't good enough for a full conviction. !!!!! btw: it took us over 90 minutes, darn near two hours, to give our verbal, written accounts and then cross interviewed by 3 game wardens of the illegal poaching activity.
the very next fall, we saw the same guys/poachers again on the same hill...and they saw us too!
When we got back to my truck, all 4 of my tires were slashed. It was one long walk down the hill from Lake Hancock and luckily 3/4 of the way down another hunter let us hitch a ride into North Bend to call from a pay phone and meet my dad; go back up to my INTL Scout, remove the damaged tires, drive back down to a local garage, purchase 3 new tires and then back up the hill to put on the 3 tires (there was one spare they didn't knife inside the locked Scout).
We reported the incident to KCP at the spur 10 gate and the Game agents too. They questioned our assumed perps when they came down to the gate but nothing was done.
The next year we saw them again. Rifle shots whistled above our heads later that morning as we still hunted the edge of a clearcut. My hunting partner grabbed me by the collar and shoved me down to the ground. He was an ex-soldier (Marine) and by the sound of the bullets whizzing by knew immediately that someone was shooting at us or slightly above our heads. I had stood there wondering what the buzzing sound was.
My father along with hunting partner to this day & myself never went back to our previously successful & treasured Lake Hancock/North Bend hills ever again.
so I fully understand this topic posters concern over turning in someone who could turn on him...