See post 250: https://boards.straightdope.com/sdmb/showpost.php?p=20945277&postcount=250
The problem with bringing things in from other threads (other boards, even) is that people who weren’t in those threads only get your selected spin on what was said. You somehow neglected to mention that I have consistently supported reparations for slavery and dramatically increasing funding for educating black kids, funding social programs that benefit African Americans, etc. Or that Obama is my favorite president, closely followed by LBJ and Grant, specifically because of their strong records of supporting civil rights for blacks.
So now someone who wasn’t in that thread might be confused and wondering how to square all this, because they weren’t there for a long and very nuanced discussion that you have cherrypicked for your ad hominem attack in an unrelated thread. And pretty soon we’re relitigating a whole different thread here. That’s why you don’t do that.
That, and the fact that what I’m saying here is either right or not on its own merits. That’s fundamental to why ad hominem is a fallacy.