You obviously have a passion to prove SDAs and any other sabbath keeping group as wrong and your fully convinced in your own mind.
Just be careful it doesn't consume you.
No, I don't
I like Jews for Jesus and the Messianic groups like Jerusalem Assembly who don't claim non-observers are in sin, but state that keeping the festivals and Sabbath has some value as a tool for learning. Both the Sabbath and the festivals pointed to Jesus, as much of the Mosaic Covenant did.
If I lived close to such a group, I'd consider fellowshipping with them because they are Christ-centered.
SDAs claim to be the remnant church, and believe other Christians are living in sin for non-observance. They can't help but believe that, due to their presuppositions.
Armstrongites, like prove-all and john832, believe the same thing, except they add on festivals. They don't even consider Sunday observers to be Christians. In addition, they believe they are going to become God beings in the resurrection, same as God the Father and Jesus Christ.
So, who would I fellowship with, if I wanted to fellowship with Sabbath and festival observers? Many of the Hebrew Roots and Messianic Jews teach that Jesus is not fully God, that Paul's writings are not inspired, and deny the Trinity, all of which I affirm. And many of them claim that non-observers are in sin, some even claiming they are not saved. And few of them have a Christ-centered focus.
I am very happy with my Evangelical Free church. They are Christ-centered and they meet on Sunday. So what? The fruit of the Spirit is plainly exhibited amongst them.
Remember, you are talking to a former Sabbath observer, for over a decade, so I have been on your side of the fence too. I see better fruits with the Sunday-meeting Evangelical Free church than I have seen with Sabbath observers.
I really like some Messianic Jews that I've met and talked with, though, particularly ones like Jews for Jesus and Jerusalem Assembly.
So, let me state it again..my issue is with Judaizers who claim others are in sin due to non-observance, not Sabbath observers who don't claim others are living in sin, and that keeping the Sabbath is a condition, requirement, or necessary fruit of salvation.