They claim they are Christian, yeah, from the surface, we could be cheated, they will come to you to "sell" Jesus Christ, if you ask them if they believe in Jesus Christ or not, they will confess they believe in Jesus, but... you should ask further if Jesus Christ is their LORD GOD or not.
In this next question, you will get the obvious answer, some of them only confess Jesus as prophet or angel.
Yeah, from this answer, it proves they're liar, no doubt !!! . Jesus and all the apostles already warned about that in the Bible clearly. You can find dozen of verses yourself. Wolf and Goat will look similiar if you're not careful. They are smart enough to undercover theirself.
The big enemy of Christianity is not other religions, but the real one is the doctrine which has "similiar" (but not same) doctrine. Therefore, to cleverly discern our enemy, you should close to WORD OF GOD (a.k.a Bible).
One of enemy of Christianity is "Jehovah Witness" or "Watchtower". Right now, this false teaching perform aggresively to reach "the lost soul". They can bring their teaching "door to door", knock your door and introduce their're Christian. Many of people devoured by them.
If you want to know what are the Jevohah Witness doctrines, here some of them:
1. There is one God in one person
2. There is no Trinity, Let God be True
3. The Holy Spirit is a force, not alive
4. Jehovah's first creation was his 'only-begotten Son'
5. Jesus was Michael the archangel who became a man
6. Jesus was only a perfect man, not God in flesh
7. Jesus did not rise from the dead in his physical body
8. Jesus was raised "not a human creature, but a spirit
and so on.. so on..
Please check others here
One of another enemy who has a big power in United States political is Mormon, a lot of famous politicians and former US Presidents are Mormon