why is it that when I think of all the people I've met that have identified as christian, the majority of them haven't been nice people?

First of all, not everyone who claims to be a Christian has been born again through faith in Christ. Secondly, even if most Christians are nasty (which is a very debatable point), it has nothing to do with whether Christianity and the Bible are true. Finally, Christians all still sin according to the Bible (1 John 1:8). The difference is they have been redeemed from the penalty of sin.

The truth is that death leads to heaven or hell, and the only way to heaven is through faith in Jesus Christ.

The Bible is very clear that no one can earn their way to heaven since good works do not pay for sins. See Gal. 2:16, Rom. 3:23-28, 4:4-5, Eph. 2:8-9, Tit. 3:5. The only way to heaven is by believing in Jesus for His free gift of eternal life. Jesus shed His blood on the cross as the full payment for our sins. He did all the work; all He requires of us is that we believe in Him. Once you believe in Jesus Christ to save you, you are secure forever!

Because we have all sinned against a perfectly holy and righteous God, we all deserve eternal separation from God in hell (Rom. 6:23). However, God loves us so much that He sent His only Son Jesus to die on the cross as our Substitute so we don't have to go to hell. Christ died for our sins, was buried, and rose from the grave three days later (1 Cor. 15:3-4). He gives eternal life freely to anyone who simply believes in Him for it. No one can be saved by doing good works. Salvation is by grace alone through faith alone in Christ alone (Eph. 2:8-9).

"Verily, verily, I say unto you, He that believeth on me hath everlasting life" (John 6:47).

You have bad karma and attractive negativity.

Its because the vast majority aren't nice.

Nothing proves that Christianity is a false religion better than the behavior of Christians.  They like to pull out their "not perfect, just forgiven" excuse whenever they're caught behaving in a decidedly un-Christlike manner, but why would anyone believe that the Christian god is real when Christians behave so badly?

"If the Spirit of Christ doesn't dwell in them then they are none of His" (Romans 8:9)

Who overthrew tables (John 215) when people were in unrighteousness!

Therefore you can't always judge a book by it's cover!

My grandfather always said: if your house burns down

and you need help, go into town. Walk past the church 

and straight to the Tavern. Fact is, that's a true statement.

We've seen variants of this shtick from atheists for years now.

There's nothing like religion to make good people do bad things.

That's sad.  The best people I know are Christians and would do ANYTHING for you.

Yes, it is the mean Christians rather than the Christ-like Christian who tend to proudly announce their faith.