I'm not saying that never happens, but those generally aren't hugely successful ad campaigns. Let's look at another successful example.Actually, I still remember Mcdonalds defensive ads after Wendy's commercials about tiny meats by old ladies.
or how Pepsi got murdered by Coke in last halloween ad.
In the Monday Night Wrestling Wars, WWF and WCW would bash each other on air constantly, as they were neck and neck. Now, once we get to about 1999, WWF stopped mentioning WCW, because they didn't need to anymore. They had pretty much won at that point. WCW would not be mentioned on air again until Vince McMahon had utterly destroyed the company and bought them up for a fraction of a fraction of what they were once worth.
Similarly, while TNA has bashed WWE many times, I don't think WWE has ever acknowledged the existence of their competitor, who is about to file for bankruptcy.