It has become fashionable among evangelical Christians to make the simplification "All sins are equal", in fact the simplification has been made so frequently and for so long that many evangelicals have forgotten (or never knew) that it was a simplification in the first place. Let me correct this by offering a more biblical account which discusses in which ways different sins may be equal, and in which ways they are not.
We tend to think of sins as the bad things that we do to other humans, but that's not the real crime (it's more of a symptom). You see the real issue is rulership. It works like this:
I decide that the present law against rape is one that I don't like, I want to break it, so I plot to overthrow the government so that I can rape people, and perhaps I rape some along the way to pass the time.
I have committed high treason and will be locked up for life because of it. You could mention the rape charges at the trial, they are serious, I deserve to be punished for them. But since I'm already getting a life sentence, the matter is a little academic.
I decide that the present law against copying a particular song by Steven Curtis Chapman is wrong. I want to break it, so I plot to overthrow the government so that I can chose my own copyright laws. And probably copy said track in the meantime, so I can listen to it while putting my coop into operation.
I have committed high treason and will be locked up for life because of it. You could mention the copyright violation at the trial, it is not all that serious, though still I deserve to be punished for it. But since I'm already getting a life sentence, the matter is a little academic.
The matter of rape is more serious than the matter of illegal copying, because the impact of rape on the victim is very high, the impact of my copying on Mr. Chapman isn't. However, both are completely overshadowed by the matter of high treason - since both equally involved trying to overthrow the rightful government to satisfy my whims both are equally high treason.
Sin, us breaking God's law, is high treason against God. We're saying 'God, I don't approve of your rule, I want to overthrow it and set up my own regime over my life'. You can see this back in the garden in Genesis 3. There the matter is made explicit: there's no other moral consequence to eating the fruit in the sense of harming other humans by it - no copyright violation or matter of rape, instead Eve is tempted to take it in order to "become like God". She's being tempted to dethrone God, to set up her own judgements in place of his ("Knowing good from evil").
So that's the sense that all sins are equal: they all have at their core the matter of high treason, all of them carry the life sentence (and all can be forgiven through and because of Jesus' death on the cross). So in terms of our standing before God after any sin, and after repentance, sins are equal.
Now of course the sins do carry different seriousness in the matter of their secondary charges, you need look no further than the Levitical law laying out the principle that the punishment should fit the crime - be proportional (the principle 'an eye for an eye, a tooth for a tooth' is a guideline for punishment given by the court on someone it had convicted. That's why when Jesus opposes it being used as an excuse for personal revenge he says 'you have heard it said' whereas whenever he's quoting from scripture as scripture he says 'it is written'. It's amazing how many people fail to read the OT bits properly and declare 'look, here's a contradiction in the Bible'). In this sense all sins are not equal - that's transparently obvious (and quite how so many evangelicals miss it I don't understand).
But from the perspective of eternity the differences are entirely academic.