It is not necessary to approve of the person or what he stands for in order to use his statements for your benefit.  I know that those who were born after, say 1965, would really like to fast forward past all of the nastiness of the "culture war" creation of the right wing.  So would I.  It is total bullshit.  But it has been effective.  Buchanan was there at the creation of this noxious meme.  To use him to undermine one of the great pillars of the neo-cons is highly appropriate from my point of view.

If you get sprayed with shit, you don't slink off and hide in shame!  You take a shower, change your clothes and get back in the fight.  It is not a question of whether the means justify the ends.  Could one have cited a Nazi to bring down Hitler in 1934, regardless of how vile that Nazi was, and one refused to do so because they feared legitimizing that person, what would be the moral content of that decision?  Means are only justifiable in terms of the ends they produce.

As the Dutch said while fighting the Spanish: "It is not necessary to have hope in order to persevere."