Can't Judge a Book by it's Cover ...

but you can judge a tree by it's fruit.

Rome and Islam have bad fruit

Judge not according to the appearance, but judge righteous judgment.

John 7:24

And think not to say within yourselves, We have Abraham to our father: for I say unto you, that God is able of these stones to raise up children unto Abraham.

And now also the axe is laid unto the root of the trees: therefore every tree which bringeth not forth good fruit is hewn down, and cast into the fire.
I indeed baptize you with water unto repentance. but he that cometh after me is mightier than I, whose shoes I am not worthy to bear: he shall baptize you with the Holy Ghost, and with fire:
Matthew 3:9

Even so every good tree bringeth forth good fruit; but a corrupt tree bringeth forth evil fruit.
A good tree cannot bring forth evil fruit, neither can a corrupt tree bring forth good fruit.
Every tree that bringeth not forth good fruit is hewn down, and cast into the fire.
Matthew 7:17

Either make the tree good, and his fruit good; or else make the tree corrupt, and his fruit corrupt: for the tree is known by his fruit

Matthew 12;33