Many religious people do find it wrong. But, many other people see nothing wrong with it.
It is a natural variance. Homosexuality in and of itself does not harm the person (last I checked plenty of straight people have stds and all that). Same sex parents are shown to be just as effective as opposite sex parents.
There is no non religious reason that stands to think bisexuality or homosexuality is wrong.
But, there is also an added bias against bisexuals, because people think they are promiscuis. Part of this comes as a result of some religious people defining orientation by behavior, and not actual orientation. They think you are only gay if you have gay sex. You are only bisexual if you are having sex with atleast two people, one of same sex one of opposite sex. And those defiinitions are wrong. Behavior is actually only a very very small part of defining orientation.
Does mankind ever agree on one thing?
No. Thus there is no supreme authority on morality especially.
Live your life comfortably, be true to yourself, introspect. Form your own morality/belief system based on this so that you may live a fulfilling, just life according to your own standards.
If you are bisexual, you're likely to say it is not wrong.
If you are heterosexual and are ingrained with traditional teachings, you're likely to say it is.
No, its not wrong and anyone who says as much is simply narrow minded and hateful. Look. You are the way you are. There's nothing wrong with that. Really, is there one single rational reason that bisexuality is "wrong" or "evil"? No. Because some god (not even the oldest god in history) says so? No.
Be who you are. You don't CHOSE your sexuality. It is what it is.
Absolutely nothing wrong with being bisexual.
What you are is not wrong, nor could it be.
If you are happy, healthy, safe and responsible, f*ck what religious people say or think.
Like they have any grip on reality to begin with. Who the hell are they to judge. Enjoy your life as you are built.
Being who you truly are is never wrong.
When humans gather together and form communities that's when things can go wrong for many because of the rules and customs that develop. Fears and injustices are always present in communities. That's just how humans -to date - are wired. Someday far in the future humans will not have these fears and life will be very different.

Nothings Wrong with Being Bisexuak
Luka Magnotta
He was amazing. Plus he did Influence music in ways that can't be measured. One thing I can say is for anyone who is a Justin Timberlake fan (and other like him) he wouldn't be in music if it wasn't for MJ.