She's writing about politics. The idea behind American politics isn't about weeding out the wishy-washy or the non-true believers. The one over-riding concept is to get as many votes as you possibly can so your guy/gal wins the election.
If Coulter is held up as a test to weed out the fence sitters or alienates moderates then she's doing conservatives harm by sending votes to the other side.
There is much more at stake than politics and votes. Regardless, much of here writings, whether some consider them too harsh or not, are quite true and and match the mindset of a good portion of Americans. I sense a fear by some that her writings may present the notion that Republicans may be "harsh". Too much concern about "appearance" IMHO.
If Coulter is held up as a test to weed out the fence sitters or alienates moderates then she's doing conservatives harm by sending votes to the other side.
If people are so moderate as to find themselves turned away from conservatism based solely on what Ann Coulter writes, then they weren't likely to vote for conservative candidates anyway. I would suggest that Ann's writings mirror the thoughts of many more people than several on this forum want to admit.