My moral standards are different than your standards. My right might be your wrong. If I think that it's ok to kill someone for stealing from me, I'm in the clear because its what I believe to be ok. Get where I'm going?

God sees all sin as one, and no one sin caries more value than another. This is so that I can't say "I'm better than him because all I did was steal, but he killed", justifying my worth to God. Who are we to claim who's better than another? To God we're all sinners, regardless of what we've done, we're redeemable.

The man who kills still has to face his consequence for his actions. He will die and suffer, but if he accepted Jesus before then, he's not getting out of his mortal punishment, but afterwards will be saved.

This is no different than those who were drug addicts, drunks, violent, molesters, etc. and they changed their life. Should you be judged on your past? Does the time between that phase in my life and the day I die matter? No, nor should it.

God doesn't want you to try to change when you accept Him. He knows what's in our hearts, and if we desire change, He will do it for us.