Court might have exercised a bit more Constitutional avoidance. Few Lanham Act disparagement claims would succeed if the manufacturers were considered limited purpose public figures.
Although the state's law doesn't distinguish personal libel from trade libel, since there are few examples of the latter in the caselaw, it is reasonable to follow the Restatement rule requiring injurious falsehood -- false statements of specific unfavorable facts -- for trade libel, a standard which requires reckless disregard of the truth.