Yeah, you can't say definitively unless they admit to it. A hat or ring is more personal though. He has thrown the one eye symbol several times and the "M" hand sign. It's hard to make that sign and kind of hurts your fingers so it's not likely to be coincidental. So when looking at this there are cases of concrete evidence and cases of circumstantial evidence which you have to take into consideration when you form your opinion. One pic of a "666" hand sign isn't enough, but when the various signs are repeated and purposeful, it's suspicious. The symbols have to be natural enough for the "profane" not to notice but standard enough for them to communicate.
As a group, there is a great deal of evidence for those in the entertainment industry and politics being Freemasons. Those in the past can be verified. It's a way for people to make the necessary connections to get ahead of the others in an industry. There are ways to get around the "atheist" prohibition. You just have to declare that you believe in a higher power and that can mean whatever you want. People aren't doing this for religious reasons, they do it get ahead on the fast track and leave the "profane" behind.
The brothers take care of each other in business, in personal life, and in court. If you throw up your hands any Masons on the jury or the bench are to acquit their brother. If you are a policeman, you give the right handshake and let your superior know you are a brother and you'll be selected over other candidates for promotions. At the least, Simon hangs out with them and isn't at all shy about being photographed with the symbol as there are many of him posing on the jet ski. Plus, as pointed out in the video by Zachary King, it's part of the program to lie, lie, lie.