Hmm, I swear quite a few ads often attack rival brands by name, and make them out as significantly worse on questionable grounds. Like many console war era ads in the gaming industry, which were very happy to tear rivals to shreds over things that didn't match reality.
So it seems there are definitely ads that attack competitors or make false statements about their products, and they don't all get banned/spark lawsuits over it.
The plaintiff would have to show that they lost revenue as a result of the false statements, which I would think would be particularly difficult to do in that case, because portrayals made openly by a competitor are not as likely to harm the reputation of the company as are portrayals made by someone who does not obviously have anything to gain from the negative portrayal. But that's just a guess.
So it seems there are definitely ads that attack competitors or make false statements about their products, and they don't all get banned/spark lawsuits over it.