Opinion.
It isn't spoiling much if people are re-sharing images, stills, gifs or moments from clips, the preview, etc that Prime itself is releasing to the public, before August 11th. If you don't want to see ANYTHING that comes from the movie before seeing it yourself, you must stay off social media.
Or block the hashtags RWRB or RWRBMovie and try your best to understand that this is fans showing their excitement and passion for the book and film. No one is trying to ruin your experience.
To me, spoiling is sharing information or content that Prime has not yet shared on any of their socials. Sharing theories is not really spoiling the movie either. If you want to be 100% surprised STAY OFF OF TUMBLR, TWITTER, INSTAGRAM, YOUTUBE, and everything else.
And if it is considered spoiling, Prime did it first (because promos happen, every now and then). They are going above and beyond in a way that I am thoroughly enjoying. If I've ever felt a moment was spoiled, it's my own fault for being on here in the first place.
Thank you!