Definition: Ad hominem abuse (also called personal abuse or personal attacks) usually involves insulting or belittling one's opponent in order to invalidate his or her argument, but can also involve pointing out factual but ostensible character flaws or actions which are irrelevant to the opponent's argument. This tactic is logically fallacious because insults and even true negative facts about the opponent's personal character have nothing to do with the logical merits of the opponent's arguments or assertions.
With that being said, allow me to give you a recent example of an ad hominem attack against Clifton Emahiser:
When I recently heard him say, and you having to correct, that he had been speaking to his Wife that afternoon, knowing she has been sadly departed for some years, my already grave doubts about his declining level of compos mentis were confirmed.
This is a ploy to discredit ANYTHING Clifton has to say on ANY given argument anymore! There are more examples of same such attacks, regarding this CRITICAL doctrinal "argument" with Eli which has caused this "schism", but what is the point? This person did not present ANY evidence to take up the argument against Clifton in a scholarly and GENTLEMANLY manner, but employed the age old ad hominem attack to COMPLETELY DISCREDIT Clifton as if to make his entire argument with Eli completely groundless! Shame on you!
In conclusion, I found this link to an excellent little essay on "Ad Hominem" which I highly suggest everyone reads. Hopefully this sheds more light on proper exegesis and scholarship: http://plover.net/~bonds/adhominem.html