Nay, Speak No Ill has a simple message, perhaps best summarized by this passage from the third verse:
Then speak no ill, but lenient be
To others’ failings as your own.
If you’re the first a fault to see,
Be not the first to make it known,
It’s all too easy to find fault in others; a single flaw often stands out more prominently than 99 virtues. Finding fault in others often serves to build our own ego, as “surely I would never do that.” We compare our own strengths with another’s weakness, building ourselves up and tearing others down.
This, of course, is in exact opposition to the Christ-like ideals we strive for. Certainly Christ was aware of the faults in those around him—he made that abundantly clear from time to time. But his primary concern was never to tear others down, but rather to encourage and strengthen the virtues he saw in others. To the woman taken in adultery, Christ said “Neither do I condemn thee; go, and sin no more.”
As I read this hymn, I was reminded of something Joseph Smith taught:
The nearer we get to our heavenly Father, the more we are disposed to look with compassion on perishing souls; we feel that we want to take them upon our shoulders, and cast their sins behind our backs. (Source)
So yes, let us speak no ill. When we see flaws in others, let’s remember our own imperfection and weakness. Instead of tearing down our brothers and sisters, let’s build them up.