Sorry, couldn't resist.
You seriously don't understand how/why a boycott works? People don't buy something from a vendor unless they agree to change something. If enough people do it, then the vendor effects changes to regain their business.
If it were organized well, and enough AMD card owners stopped buying particular games because they ran poorly on AMD cards, relative to nVidia cards, the game producers would care. Seems suspicious to me that the vast majority of top titles run comparatively with both brands, but a few titles are outliers. These games are broken in some way. When you see one company's logo, either nVidia or AMD, flashed all over the game and it runs like crap on the other vendor's card, people wonder if it's done purposely. When you have documented examples of it happening in the past, it just adds to the suspicion.