Yes and no.
Often Christians say, when discussing things like abortion and homosexuality, that these are sins just as lying, gossip, and gluttony are sins. (I say it sometimes.) This is usually because we want to show that we’re not better than homosexuals or people who have been involved in an abortion. We’re placing ourselves in the “sinners” category, right where we belong.
It’s true, in one sense, that a sin is a sin. Every sin is the same in that it’s an offense against a holy God, and deserves his punishment. But is every sin “the same”– that is, equally offensive to God? The Bible’s answer is no.
This is one of many questions where the Westminster Confession and its catechisms are really helpful. Question 84 of the Shorter Catechism shows us how every sin is the same:
Q 84. What doth every sin deserve?
The previous question shows how every sin is not the same:
Q 83. Are all transgressions of the law equally heinous?
Question 151 of the Larger Catechism (scroll down and click “Q. 151-196”), which is longer than many of my posts, gives many examples of the “several aggravations” that can make some sins worse than others, with lots of Scripture citations. It’s well worth a 5-minute read.
So while it’s important for us to take our seat among the sinners, we should also feel free to say that some sins (including some of our own) are much worse than other sins. For example, it’s a sin for a man to speak harshly to his children because he can’t control his temper, but it’s a much greater sin for him to pay to have his unborn child killed so he’s free of the inconvenience that child might bring.