Kevin.  Here is the text from the FMA that I presume you support (please correct me if I'm wrong).

Marriage in the United States shall consist only of the union of a man and a woman. Neither this Constitution or the constitution of any state, nor state or federal law, shall be construed to require that marital status or the legal incidents thereof be conferred upon unmarried couples or groups.

If this amendment were to pass - then what you're using as a bright-side argument (ie. civil unions) would be wiped out as well.  As you know, civil unions are in place for people to be able to receive the rights (hospital visitation, insurance claims, right to sue, custody, property ownership, etc) that bona-fide married couples get.  This amendment specifically bars un-married couples from receiving anything resembling what married couples get.  Twist it and stuff it in your sack anyway you want - but this amendment is prejudice in black and white.  Bush might say he's for civil unions, but obviously he hasn't even read the amendment he's supporting.

And as to your side jab at Kerry and Edwards - they support civil unions voted on by states but do not support an amendment to the US constitution that legitimizes discrimination.  Your man does.

Dan