I mean that it might be argued that a polygamist can take advantage of the tax code by taking multiple wives, circumventing any tax responsibility by grabbing up as many tax exemptions (aka wives) as possible.
The 2nd Amendment grants the right to bear arms. It doesn't force people to own a gun. It doesn't force someone to shoot another person. Laws against murder prevent you from choosing to shoot someone you don't like.
The 1st Amendment grants freedom of religion, it doesn't force people to choose a religion. It grants freedom of speech, it doesn't force people to say any thing. It grants freedom of assembly, it doesn't force people to assemble.
Even if being gay is a choice (and most don't believe it is), this nation is a nation of freedom and the freedom to choose the way you live your life up to the point that the way you live your life has a negative impact on the rights of others. Who someone chooses to marry has no negative impact on your life or anyone else's.
Eliminating DOMA doesn't force you to do anything. You can still think gays are icky people all you like. You do not have to attend a gay wedding or give gay couples wedding gifts. You don't even have to acknowledge that they are married (just as the Catholic Church doesn't acknowledge second marriages if their member gets divorced).
But we also recognize a "right to education" that in effect secures an entitlement based on a moral/societal belief in the importance of education. It's hard to see how this right protects choice - on the contrary, it limits choice in that it burdens the population to provide this benefit (it conflicts with our right to liberty).
The right to free speech derives from natural law and protects from the actions of others, whereas the right to education derives from legislation and puts obligations on others.
But those natural freedoms don't grant a right to civil marriage, which (like the right to education), is a moral/social creation that grants certain benefits and protections. By its very definition, civil marriage in fact does "force" people to do a lot of things in that they are required by law to respect that right. Whether or not it has a negative impact on anyone's life seems largely irrelevant from a legal perspective.
Equal rights for a lifestyle choice based on "freedom to choose the way you live your life up to the point that the way you live your life has a negative impact on the rights of others" exists right now, unless you know of any laws prohibiting such activity.
When it comes to equal rights for a civil right to marriage, however, "freedom to choose the way you live your life" provides no more justification for gay marriage than it does for a wealthy white man to claim rights to affirmative action.
I know some people who would get married to someone they didn't love intimately, even someone of the same sex, just because the marriage would benefit the two of them in some way or another, either financially, emotionally, or both.
"A woman is like a teabag, you never know how strong she is until she gets in hot water." - Eleanor Roosevelt
Keep your religion out of other people's marriages.