Again, I'm sorry, but the irony of this is just staggering. One of the biggest, most well known deities in Forgotten Realms started in Greyhawk. Lolth and all things Drow is a Greyhawk invention that was ported, pretty much whole cloth, from Greyhawk into the Realms. The most popular character in FR owes his entire schtick to Greyhawk.
Since when didn't FR beg, borrow or outright steal material from other settings? So much of Greyhawk and other settings - never minding things like Kara Tur which is just rebranded Oriental Adventures, straight from Greyhawk, or Al Quadim (sp) which is ported directly into FR, or heck, even Waterdeep borrows pretty heavily from the City of Greyhawk (hidden leaders, for example) - have been dropped into FR that it's pretty impossible to claim that you could undermine anything.
FR has been the baseline setting for D&D for about thirty years now. Certainly since the day Gygax left TSR. Virtually everything that was made by TSR eventually got dumped somewhere in the Realms.
I always thought that was the main draw of the Realms to be honest.