I mean, c'mon man… you don't own the rivers, and if somebody reads on a message board somewhere about the productive water or the hot hatch, why would you get all bent out of shape? You're a pro, right? Up your game. That's not to say that it's ever okay for someone to poach water or low-hole another angler. That's particularly uncool when guides do it. I've seen that happen too.
The best trout guides don't worry about such matters. One of the best I have fished with, Kea Hause of Colorado's Roaring Fork Valley, once explained to me why he believes a great guide should be an open book. The way he sees it, clients pay guides to become better anglers. Sure, catching fish is a major part of that. Teaching skills is probably even more important. And arming people with information to fish on their own is also key. Hause said he has been on some trips where his boots barely got wet. Instead, he and his sports sat around a picnic table looking at and marking maps. That's what they wanted. That's what they paid for. So he gave it to them. He figures that people will find information anyway. Best to arm them with the right information, and have everyone spread out, rather than pounding the same popular water, over and over.