Animal abuse is illegal, probably on the state level. I don't really see why we need a federal law stating that if you record and publish that same abuse, you break another law.
Same reason as child porn is illegal.
Some things society wants to stop, it's much more effective to ban side things because of enforcibility.
If you can help dry up the market for the images to the sick customers who pay for the industry to make them, you can reduce the abuses from happening.
It's a little like cities with laws against drug paraphenilia.
The thing is to draw the line short of where legitimate rights are infringed. Should it be illegal for someone to publish an article saying they used drugs and enjoyed it? No.
I started out to say I was in favor of this law, but somehow the line has to be drawn short of banning people who public documentary evidence for political reasons on the topic.
I'm not sure how exactly that can be worded, and if they don't find the wording, they need to err on the side of more free speech than less and concentrate on the abusers.