Several people have graciously participated in this debate by emailing me their thoughts.
I have included here portions of some of those emails, along with portions of any responses I sent.
If you haven't read the "Three Reasons," click here
These are arranged with the emailer's comments, and then mine.

emailer 1:
I read with interest your "Three Reasons" and I respect your take on it. You sound like a political scientist. You are right—the checks and balances was designed in such a manner to make our government operate with safeguards. However, reality says it's not happening. Though social engineering is not in the judicial job description, we know that activist courts do twist the Constitution to push a liberal agenda. So, they are already meddling with marriage. Truth is, the Constitution is already being amended, not by democratic process, but by judicial decree. And Congress will not impeach, but rather many encourage them. I don' t believe it evil to amend the Constitution (I believe it was last amended with the 27th in 1992-- for "congressional compensation")!

me:
Certainly there is nothing evil in amending the Constitution. The amendment process was conceived because the signers knew adjustments might need to be made. However, the purpose of the Constitution should remain exclusively to define federal structure and power. The 27th Amendment did concern Congressional pay, but so does Article I, Section 6 of the Constitution. The Constitution gave Congress the power to set Congressional pay. The 27th Amendment made pay changes not become effective until after elections. So, today's Congress can give a pay raise to the next Congress, but not themselves. Gay marriage is a more significant issue, but Congressional pay is a Constitutional issue.

emailer 2: (note: This email refers to me in the third-person because it was funneled through a third party who sent my Three Reasons to the emailer. My response was also funneled. :-)
Bruce is absolutely right from a libertarian viewpoint. I can not disagree with his philosophy at all. The problem I have with not supporting the marriage amendment is finding a viable alternative in today's America. The government is into everything we do. I doubt if much of that will change in our lifetime in any orderly process.

me:
[He] echoed the same sentiment as [another]. "While it's fine and dandy to talk about what should be and what the Constitution is supposed to be, it's not realistic." I agree that it would be a long, hard, maybe impossible battle. But, it's the right battle. Taking the pragmatic way, and going with an Amendment, simply pushes us further down the road to tyranny. We're just hoping that we'll be the tyrants. Well, if I read the Bible properly, it says we're not going to be in control and our enemies will gain the power. And what will be our basis for complaint when they abuse us with the power we created? It will be like Israel crying out to God for relief from the kings they demanded God give them (see 1 Sam 8:6-18).

emailer 3:
[This] phrase also brings fear to some, "remains within our churches." Even today some of our "churches" have lost their way and condone what God condemns. And you have to realize that the term "church" has also been defined by the government. It encompasses more than the biblical meaning of "the church." After all devil worshipers can have a "church" with their definition. That's a scary thought.

me:
You're right that church means different things to different people, and some churches are not what we think of as church. But, if the government wasn't involved, you would not be forced into accepting those ideas. As I wrote in the Three Reasons, anyone would be free to call themselves married, just as they're free to call themselves Martians. That doesn't mean we have to call them Martians or married, though. When two men tell us they're married, we can shake our heads and say "whatever." And when some tell us their church performs gay marriages, we can politely ask, "And where's your church located, Laodicea?"

emailer 4 (note: This person is one of the dozen or so friends who have previously sent me an email advocating some sort of support for the FMA. I responded to those who sent me such emails by sending them my Three Reasons. This is the response I received. I debated whether to include it here, since it's so...je ne sais quoi. I decided to include it because so far it's the only truly negative response I've received and it provides a contrast to the others.)
You are full of it!!!! Take me out of your address book!

me:
I know you told me to take you out of my address book, but I don't want this issue to cause a rift between us. Is our point of disagreement that serious? Even though we disagree on the FMA, I think we should both be able to recognize each other's sincere desire to bring glory to God through our actions. Can we discuss this?

emailer 5 (note: This is a response to an email I sent to one my old seminary professors.)
You are correct. There is no debate in SBC circles. For most SBC folks to even imagine that there would be space for proper debate of
this would be mind-blowing.... I've been doing a great deal of thinking about the FMA for the past 2 weeks. I think that you have most closely articulated what I think. Have you seen any published arguments from Christians that coincide with yours? Thanks so much for taking the time to think about it and write about it. I think of you and pray for you and Jennifer often.

emailer 6
We appreciate your sharing in this matter that is most important and should be handled in the BEST way! We too are unsure if the Amendment Process is the BEST for everyone and everything concerned.

emailer 7
Thanks for the different "take" on Marriage amendment. We appreciate you and the areas of service you provide for the Lord….