Final answer:
The persuasive tactic described, which suggests "everyone" is buying a product, is known as the bandwagon fallacy. It is a common advertising and propaganda technique that plays on the audience's fear of missing out.
Step-by-step explanation:
To identify the type of persuasive tactic being employed in the line from an ad, one must consider the characteristics of various rhetorical devices. A common persuasive method is the bandwagon tactic. This involves creating a sense that "everyone" is buying or doing something, which may make others feel compelled to follow suit to avoid being left out. Another common technique is creating fear, where the ad may suggest that not using a product or service could lead to negative consequences. Persistence and repetition involve the recurring presentation of an idea or product to embed it in the audience's memory. Lastly, glittering generalities use vague, emotionally appealing words that have different positive connotations for individual people but no concrete, specific arguments.
Given the description in the question, the tactic of asserting that everyone is buying a product leans heavily towards the bandwagon fallacy. This rhetorical strategy is often used in advertising and propaganda to try and convince people that a high volume of others embracing a product justifies its purchase, implying a fear of missing out (FOMO), which is an emotional trigger.