To be charged with slander/defamation the prosecutor must prove you were TRYING to "damage the reputation"....
Read below, it must be proven that what you said about the business or product is untrue...
Where a person's goods are brought into discredit, rather than suing for defamation, the tort of injurious falsehood or slander of goods would be applied (See Flaman Wholesale v. Firman et al (1982), 17 Sask. R. 305). This tort; however, requires proof of monetary damages. This has become prominent in Cyberspace as disgruntled ex-employees or dissatisfied customers have taken to posting complaints along with defamatory statements on the web. For the plaintiff, this tort is available where: first there was a statement made about the plaintiff's goods; second that the statement was false; third that the statement was published maliciously (dishonestly with improper motive); and lastly, that the plaintiff suffered special damage.
Dietrich further notes that in Canada, legitimate comparisons between products are generally not actionable. However, the distinction between disparaging comments and truthful comparisons is often a fine one and the test used to identify when a statement constitutes slander of goods involves determining what a reasonable person with knowledge of the facts would conclude. (17) In order to be liable the defendant need not necessarily named the plaintiff or the product(s) directly but rather where an implication will be drawn by the public that the defendant's disparaging comments must necessarily have been referring to the plaintiff's product (for instance when there are only two products in a market).(18)