It depends on what he is lying about and why he had to lie.
For example, if a random person asks me about my gender, where I live, how much btc I have.. then I may lie to him (in most cases I would simply ignore him because that's none of his business. I this case, lying didn't cause any harm and it was necessary to protect my privacy.

However, if am selling a product or offering a paid service and I lie about the qualities of that product/service with the intent to deceive the consumer then, in this case, a red tag is completely justified.