Gays plan babies - so no gay marriage?

Wow, what a strange read this is. Some conservative lawyer in the US (a Paul Clement) has come up with a new reason not to allow gay marriage:

But if you’re a lawyer defending a gay-marriage ban in court, you need an actual legal reason for your position. This was the unenviable spot in which Paul Clement found himself recently, defending the House Republican opposition to gay marriage before the Supreme Court. Clement developed a reputation as a right-wing superlawyer for his work in transforming the legal challenge against Obamacare from a no-hope libertarian crusade into very, very nearly the law of the land. It’s a measure of the hopeless illogic of the case against gay marriage rather than Clement’s lack of skill that the best legal case he could come up with was … well, it wasn’t good: 

Marriage should be limited to unions of a man and a woman because they alone can "produce unplanned and unintended offspring," opponents of gay marriage have told the Supreme Court. 

By contrast, when same-sex couples decide to have children, "substantial advance planning is required," said Paul D. Clement, a lawyer for House Republicans. more

Um,,,,what? That's it? Because gays plan their babies they shouldn't be allowed to get married? Fuckin hell man, that's really clutching at straws.

What about straight people who have to go through IVF to have a baby then? Should they be banned from marriage as well? 

How the hell could this guy say this crap in front of people, and keep a straight face?