Hello!
Some people here I know, some I don't. Hi to all.
I'm Catholic. The best information anyone has ever had (care to dispute that?) says that Peter did indeed die that way.
That's why Catholics use that symbol. There have been plenty of Christian martyrs whos died on crosses, but it's not appropriate to use a right-side-up cross to represent anyone else's death for obvious reasons.
Only Peter's cross is usd symbolically, because it cannot be mistaken for Jesus'.
There's no Satanic connection to this, that's 18th century racist hysteria you've dug up, there.
Cheers!