Is ignorance a sin? No, and yes.
Let’s define ignorance. To be ignorant means that you do not know. It’s a lack of information, often a lack of awareness. Both logically and empirically, we acknowledge that we do not know all things. None of us are omniscient, which means we are ignorant. It’s not whether or not we’re ignorant, but how much so. There’s no sin in being finite.
There is another consideration. It’s not just how ignorant we are, as in, to what degree we are unaware, but also more importantly for this exhortation, why are we unaware?
It’s one thing to be a child, it’s another thing to act childish because we hate how hard adulting is. It’s one thing not to know, it’s another thing to become an ostrich and stick your head in the sand; “No way I’m looking at that!” You know enough to know that you don’t want to know. And that willful ignorance is oftentimes sin.
Jesus said that those who crucified Him did not “know what they do,” and that required forgiveness (Luke 23:32). Paul said that he “had acted ignorantly” when blaspheming and persecuting, but that required mercy and grace (1 Timothy 1:13).
If you say, “I don’t know how to do brain surgery,” no harm done (as long as you don’t try to operate). If you say, “I don’t know what happens in Planned Parenthood,” you are doing harm upon harm. You may be covering cowardice, or laziness, maybe even adding lies to the mix.
The good news is that Jesus died for all our sins. Christ died for those who turned from sacrificing their children to Molech. Christ died for David who with a contrite heart sought mercy for his adultery and murder. Christ Jesus came into the world to save ignorant and insolent sinners.