Abortion analogies and credibility

On the topic of the language we use to describe legalized abortion (see, e.g., here, here, here, here, here, here, and here) a reader writes:

In my opinion, there is a Gresham's law of language in which the attempt to inappropriately exploit the connotative power of a word has the opposite effect of diluting its ability to convey any meaning at all.  What's more, since most people do not believe that the intentional killing of a 12 year old child and the act of abortion are morally equivalent, the unintended result is not only to debase the word, but to reduce the speaker's credibility as well -- just as we would look down on someone trying to pass off counterfeit goods.

UPDATE: Another reader responds:

It may be the case that calling abortion a "holocaust" or some other similar term reduces a pro-life advocate's effectiveness, but that does not mean that such a term does not reflect reality.  Take an example: holding up large pictures of aborted children may churn some onlookers stomach's and cause them to disengage from the issue rather than confront it.  But the reality of in what abortion results is no less accurate.  Reality is not defined by the reaction people have to those who speak facts.  I think we should be clear on just what we are debating.  Is it "These terms don't help" vs "Yes they do" or the much different debate of "These terms do not reflect reality" vs. "Yes they do"?

Can we so easily separate reality from effectiveness, though?  After all, when we're talking about analogies, we're not talking about literal reality.  Legalized abortion is not the Holocaust.  If we want to call it the Holocaust, isn't that decision motivated, in significant part, by our perception of persuasive similarities?