airtight argument

There is no such thing as an airtight argument for a bad choice-not if the argument is made with a modicum of honesty.

They're belaboring a point, trying to create this airtight argument, when if you just got to your point in a more direct manner it would be stronger.

Not an airtight argument (all anti-discrimination laws pick and choose among protected classes), but a cleverly textualist one--and one that seems to have helped convince a majority of the court to strike down the amendment, despite a lack of helpful precedent.