There are certainly notable examples of proponents of traditional marriage who have not lived up to their vows but it's a real stretch to suggest that "so many of the very loudest defenders...are the worst at keeping their vows."
Clearly this is simply an impression you have formed based upon your personal bias.
I'm good with same sex marriages, but I don't see how opposing them necessarily demands fidelity in the relationships of the opponents.
If the opponent's argument is based on morality then he or she would be wide open to charges of hypocrisy, if fidelity was of no value in their relationships.
All arguments for traditional marriage, however, are not based on morality.
Promoting traditional marriage between a man and a woman is a very conservative concept. Traditional marriages have been the norm for thousands of years, and if one believes that the basic family unit is the
building block of societies, one is likely to be concerned about fiddling with its basic construction.
Why do you want to see "the religious" have better morals than "the rest of us?"
There is an implication here that you expect immorality from the non-religious, but are disappointed when those who claim to be religious make the same mistakes. You're not a closet zealot are you?
Since when are "the religious" required to be saints?
While their religiosity may compel them to strive harder for a thoroughly moral life, it certainly doesn't provide (nor demands) assurance that they will succeed.
Those who genuinely strive to abide by a moral code and fail have not proven themselves to be immoral hypocrites, but human. Is it, somehow, preferable for those who fail a test of morality to have never strived to pass it?
Is it somehow honorable for the immoral among us to engage in their anti-social behavior while refuting any moral code?
This is the sort of bent philosophy of which so many Liberals seem bound to promote:
If you make no pretense to being moral, your immorality is at least authentic and in some way admirable.
On the other hand if you subscribe to a moral code and come up short in terms of compliance, you are a hypocrite and somehow worse that the guy described above.
What is truly ironic in terms of this issue is that while legally recognized same sex marriages are a Holy Grail for Liberals, stable, long term marriages are not.
Before too long, same sex marriages will be generally accepted, and become something of a norm. Once that happens however, the novelty will have worn off and we will see just as many gay people with multiple, frivolous marriages as we now see with heterosexuals.
How ironic that in an age when so many heterosexual couples don't see a whole lot of substantive value in marriage, homosexual couples feel they have to fight for the right.
By and large, homosexual couples are not really different than their heterosexual counterparts. I doubt they are any more or less inclined to infidelity, nor perceive, to a greater degree, that marriage is a sanctified holy union of two people.
Once they win
and get to marry they will quickly slip into the statistical pattern of heterosexual couples. Divorces will be common place and "living together" will be favored prerequisite to wedlock.
Oh how we long for that which we cannot have.