People have such opinions because of members like the one in this video: [
link]
Starting at around 0:16 he says,
"I am Lucifer". When asked to define Lucifer, he says,
"pure, virtuous, wholesome, innocent individual that's out to help people." And at around 1:34 we see his masonic... hat? I'm not sure what that is. Any group / individual calling the devil "innocent and virtuous" obviously adores/holds in high esteem/worships the devil. Even though I don't agree that Lucifer is the devil's name, that is who most people are referring to when they say "Lucifer" (the devil, satan, prince of the world, prince of the powers of the air). That (amongst other examples) is where the Free Masons get the Satanic allegations. If they don't worship the Creator (YHWH/Jesus), it will be labeled Satanic. Note: he was pretty oblivious to what the biblical Jesus said; so, no, he's not a Christian.