A person commits an offense if, with intent to
    injure a candidate or influence the result of an
    election, the person enters into a contract or
    other agreement to print, publish, or broadcast
    political advertising that purports to emanate
    from a source other than its true source.

This seems to be the key issue. It seems unlikely that a prosecutor could achieve a conviction under these laws, given the specific meaning of some of the terms used (as defined in §251.001). I haven't seen the video, but it sounds like it was a general parody of the NRA?

At any rate, a prosecutor would have to prove that:

1. The creator of the video has specific intent to harm a particular candidate, or otherwise influence the election result.

2. The latter part of #1 (influence result) seems to be made irrelevant by the definition of 'political advertisement': "...means a communication supporting or opposing a candidate for nomination or election to a public office or office of a political party, a political party, a public officer" [§251.001 (16)]

1. The Yes Men is assumedly not paying to promote this video (so it's not "an ad"), 2. The message is not electioneering.

We're used to seeing, "paid for by" and "I approved this..." messaging in electioneering ads that are regulated by the FEC. The NRA, a 501(c)(4), has to play by different rules to keep its status.

IANAL, but I'd assume that the NRA would need to argue that the video puts their 501(c)(4) status at risk to warrant legal action outside of just playing the copyright/damages card.

But it also has a PAC, the Political Victory Fund, which is quite able to do the usual stuff, here's their first TV ad for this election they just cut, I've set the time to the last 5 seconds where they claim it per the law: https://youtu.be/SIl20jItjHY?t=25