Is it possible for a true Christian to recognize a false Christian?

 I have read where many professing Christians say that no one can say if another has the Holy Spirit or not because they say only GOD knows. Some say you can believe in your own idea of who GOD and Christ are, that this doesn’t matter.  That theology is not important only that you love one another. The Jehovahs witnesses teach love one another and say only the FATHER is GOD but Jesus is Michael the angel. Hey no problem there right ?  Who cares, they believe in a GOD and Jesus plus love one another so they are Christians.  If you have left them perhaps you should return.  If you love and they love then why are they the target of rebukes, rebuttals and debunkers ?  Is that love ?  

Matthew 7:15,16,17,18,19,20

What did Jesus mean by fruit ?  

Matthew 7:21,22,23  Would these people be Christians?

Matthew 24:24   Luke 13:25,26,27  2 Corinthians 11:13,14,15   1 John 4:1  Why bother trying spirits if you can’t identify who a true Christian is ?  2 Peter 2:1   Do these scriptures prove that anyone who says Jesus is Lord is a Christian ?  How about people who preach false doctrine?  2 Corinthians 11:3,4  Anyone that “puts up” with false doctrine Paul was afraid for them.

Of all things that prove the identity of a true Christian is GODS love in them.  John 13:35

So then, there are two main things that identify a true Christian; understanding the truth and loving with GODLY love.  Now of the two of these Godly Love is greatest.  1 Corinthians 13:2  

If someone is worshiping an idol are they a Christian?  Is the trinity an idol ?  Does GODS spirit teach Christians lies ?  Is the immortal soul a lie, is Jesus said to be GOD a lie, is once saved always saved a lie ?  Scripture says,  Romans 8:9 , so then a person who worships something that is not GOD, and believes in many lies some say has the Holy Spirit and is their brother or sister.  Colossians 1:2  There are faithful brothers and sisters in Christ but also the brotherhood “in the world” and this means the carnal unconverted people in the world. The “in the world” is not the church because the church is not of the world.  1 Peter 5:9  Why would Jesus say, “do not give what is holy to dogs or cast not your pearls before swine ?  How about,  Galatians 2:4  2 Corinthians 11:26  Jude 1:4   Romans 16:17,18   There are false brothers and sisters pretending to be Christians.   Should true Christians say they are our brothers and sisters in Christ?  To be clear true Christians do love all people but not all of them are your brothers and sisters in Christ.  

However, if you disagree that’s OK, I’ll understand why.