I think "side-drifting" in the context of this article is more of a metaphor about instant gratification... than the actual act itself. It's the selfish, greedy, "hey look at me... I can catch a ton of steelhead so I must be a great fisherman" attitude that he is railing against more than anything else.

We've all seen it out there... the low-holing, bad ettiquette and pompous bravado displayed by a lot of guys. I bet If Herzog ran into a conscientious side-drifter who was polite and not out to catch every fish in the river then brag about it on the Internet... he wouldn't think ill of him/her at all.

That's just my take on it.