Reply #10: Debate them for many reasons:

[Swamp Rat]

1. It might change their minds (if they have one).

2. It might make them angry, upset, confused, which can lead to different outcomes:
A. They might change their minds later on.
B. They may become so discouraged they do not vote for a republican.
C. They may become so discouraged they do not vote at all.
D. They become so discouraged they might even vote for a democrat out of spite (as per Rash Limpball's suggestion).
E. They may get so angry they become even more radicalized, thus damaging and dividing the GOP.

3. Their heads might explode, thus saving more oxygen for the rest of us.