how it gives Nvidia hardware an advantage in a lot of games
Except it really doesn't. The only Gameworks effect that chugged on AMD hardware was Hairworks. That's just the nature of Hairworks, it's heavy tessellation that makes the hair/fur look more realistic and react more realistically. AMD cards just aren't as good at tessellation as Nvidia cards, namely Maxwell.
People have managed to twist Maxwell's increased performance into some sort conspiracy about how Nvidia is purposefully running effects at a higher then necessary level to get people to buy their new tech.
*Second, Nvidia doesn't have to do that. The Maxwell architecture is just better at these things. Why? Because it's a new architecture!!
Nvidia went back to drawing boards and made some major changes with GM204. Maxwell is just superior technology and is more capable at running these effects than Kepler and GCN. Nvidia doesn't have to "sabotage" Kepler and GCN to make Maxwell more appealing. Maxwell's blatantly superior performance with these effects and even with them disabled is good enough.
As for AMD, I really don't see how they or the people in these pc gaming subreddits can say the other Gameworks effects are even affecting them, let alone sabotaging them. Every single Gameworks effect has been optional. If there was some big plot by Nvidia, surely they could come up with a better plan that couldn't be thwarted with the click of a button?
Also, all the VisualFX are scalable. Meaning that there is nothing stopping devs from changing these features, regardless of what some people believe or have been told. Gameworks is a source licensing middleware/parnership program. Devs bought a license or became a Gameworks partner to get the source code for scalable features. There is no non exclusive Gameworks tech that cannot be optimized for Amd or less capable systems. (I.E. Enhanced Rain Effects in Arkham Knight running on consoles.)
Gameworks is a non issue that AMD have been using as the perfect scapegoat. Project Cars, the supposed "best" example of Nvidia's sabotage was actually the fault of AMD's drivers. AMD has well known cpu overhead issues and lackluster dx11 support. AMD users on win 10 didn't have these performance issues. Of course they're not going to admit this, so they decided to blame Nvidia. They have nothing to lose by playing victim.
All of this anger is the result of a dying company reaching at anything and everything they can to keep their head above water.