When "lying" is a meaningless accusation
I have always defended the use of the word "liar," because it is necessary to hold people accountable when they distort facts or actively fabricate things to smear others. Pointing out that a liar actually is a liar is not only not uncivil, it protects civility in the public sphere because lies are destructive. However, far too often the accusation of "lying" is merely a way to say "I disagree with this person."
One of the comments on my most recent letter to the editor was that "equating embryos with babies" is an "outright lie." So if this man speaks to a pregnant woman who says something about her "baby," does he calls her a liar? What about the woman's husband? Does he call the father a liar? Of course, unless you are a total fanatic, you would not do that. I presume that if this person sees a woman being comforted after a miscarriage, he would not break out the word "liar" if someone expresses sadness (or if the woman herself expresses sadness) over her "losing her baby" - unless he is a total monster.
As far as the word "embryo," that itself is dishonest. You can point to official definitions of medical textbooks all you want, but the vast majority of people think of an "embryo" as an undifferentiated clump of cells. When a surgical abortion takes place, the "embryo" is very clearly not that. You can see arms and legs and a head - tiny to be sure, but not a clump of cells. By the time most abortions take place, the "embryo" has crossed the stage of development where she is officially a "fetus" anyway.
Ultimately, though, accusing someone of "lying" is meaningless if the accusation is over a difference of opinion - and like it or not, that is what this is. Some argue that the proper word is "embryo" or "fetus" depending on gestational age, but the fact that others do not does not mean they are guilty of an "outright lie." Not only does this poison the well and contribute to an uncivil exchange, it actually damages the accuser's credibility. If you are known for calling differences of opinions "lies," you are less likely to be taken seriously when you confront an actual lie. Who does that benefit? Actual liars.